Bài 13: Class trong Java (tiếp)

<span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Sau bài viết này, các bạn sẽ có cái nhìn toàn diện hơn về </span>class<span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> trong 1 project Java (interface, abstract class tương tự), các bạn áp dụng để viết code sao cho dễ nhìn dễ hiểu và dễ quản lý. Chọn cách viết nào cho phù hợp với từng bài tập, từng project. Sau bài này, các bạn cũng sẽ hiểu hơn về lập trình hướng đối tượng trong java.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;">1, Bài có 1 class, dùng class chứa hàm main!</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Khi bạn lên mạng, tìm code, bạn sẽ thấy người ta thường dùng cách này</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Thường có 1 class duy nhất. Cách viết này thường dùng để chia sẻ thuật toán, cú pháp hoặc giới thiệu các phương thức của 1 đối tượng trong thư viện nào đó.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 1:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> Một bài tập quản lý sinh viên nhỏ:</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;">package sinh</span><span style="color: #007700;">.</span><span style="color: #0000bb;">vien</span><span style="color: #007700;">;<br /><br />public class </span><span style="color: #0000bb;">SinhVien </span><span style="color: #007700;">{<br /><br />    public </span><span style="color: #0000bb;">String hoTen</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int namSinh</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">float toan</span><span style="color: #007700;">, </span><span style="color: #0000bb;">ly</span><span style="color: #007700;">, </span><span style="color: #0000bb;">hoa</span><span style="color: #007700;">;<br /><br />    public static </span><span style="color: #0000bb;">void main</span><span style="color: #007700;">(</span><span style="color: #0000bb;">String</span><span style="color: #007700;">[] </span><span style="color: #0000bb;">args</span><span style="color: #007700;">) {<br />        </span><span style="color: #0000bb;">SinhVien a </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">SinhVien</span><span style="color: #007700;">();<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoTen </span><span style="color: #007700;">= </span><span style="color: #dd0000;">"Vũ Văn A"</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">namSinh </span><span style="color: #007700;">= </span><span style="color: #0000bb;">1992</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">toan </span><span style="color: #007700;">= </span><span style="color: #0000bb;">10.0f</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">ly </span><span style="color: #007700;">= </span><span style="color: #0000bb;">9.0f</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoa </span><span style="color: #007700;">= </span><span style="color: #0000bb;">9.5f</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">println</span><span style="color: #007700;">(</span><span style="color: #dd0000;">"Điểm Tb là: " </span><span style="color: #007700;">+ (float) (</span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">toan </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">ly </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoa</span><span style="color: #007700;">) / </span><span style="color: #0000bb;">3</span><span style="color: #007700;">);<br />    }<br />}</span></span></code></div></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Khi làm bài tập hoặc làm các project, ít khi dùng cách này, nó không hay cho việc quản lý, giới thiệu để các bạn có thể đọc và hiểu nếu như gặp phải những bài chia sẻ dạng trên!</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;">2, Class đặt cùng file class chứa hàm main</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Vị trí đặt ngoài class chứa chương trình chính, ở bài trước, mình có viết ví dụ theo cách này! Nó chỉ thích hợp với bài ít class, class ít thuộc tính và phương thức. Nếu bài có nhiều class, mỗi class có nhiều phương thức, điều này cũng không tốt, sẽ rất khó nhìn và quản lý cũng như nâng cấp!</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 2:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> Nội dung bài như ở Vd1, bổ sung thêm class giảng viên, nhưng sẽ bố trí lại vị trí class như sau:</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;">package truong</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoc</span><span style="color: #007700;">;<br /><br />class </span><span style="color: #0000bb;">SinhVien </span><span style="color: #007700;">{<br /><br />    public </span><span style="color: #0000bb;">String hoTen</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int namSinh</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">float toan</span><span style="color: #007700;">, </span><span style="color: #0000bb;">ly</span><span style="color: #007700;">, </span><span style="color: #0000bb;">hoa</span><span style="color: #007700;">;<br />}<br /><br />class </span><span style="color: #0000bb;">GiangVien </span><span style="color: #007700;">{<br /><br />    public </span><span style="color: #0000bb;">String hoTen</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int namSinh</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">String mon</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int luong</span><span style="color: #007700;">;<br />}<br /><br />public class </span><span style="color: #0000bb;">Main </span><span style="color: #007700;">{<br /><br />    public static </span><span style="color: #0000bb;">void main</span><span style="color: #007700;">(</span><span style="color: #0000bb;">String</span><span style="color: #007700;">[] </span><span style="color: #0000bb;">args</span><span style="color: #007700;">) {<br />        </span><span style="color: #0000bb;">SinhVien a </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">SinhVien</span><span style="color: #007700;">();<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoTen </span><span style="color: #007700;">= </span><span style="color: #dd0000;">"Vũ Văn A"</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">namSinh </span><span style="color: #007700;">= </span><span style="color: #0000bb;">1992</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">toan </span><span style="color: #007700;">= </span><span style="color: #0000bb;">10.0f</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">ly </span><span style="color: #007700;">= </span><span style="color: #0000bb;">9.0f</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoa </span><span style="color: #007700;">= </span><span style="color: #0000bb;">9.5f</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">println</span><span style="color: #007700;">(</span><span style="color: #dd0000;">"Điểm Tb là: " </span><span style="color: #007700;">+ (float) (</span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">toan </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">ly </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoa</span><span style="color: #007700;">) / </span><span style="color: #0000bb;">3</span><span style="color: #007700;">);<br /><br />        </span><span style="color: #0000bb;">GiangVien gv1 </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">GiangVien</span><span style="color: #007700;">();<br />    }<br />}</span></span></code></div></div><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Chú ý: </b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Chương trình vẫn chạy nếu bạn để các class SinhVien và GiangVien ở phía cuối chương trình, chỉ cần nằm ngoài class Main là được</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: red; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"><span style="font-size: medium;">3, Mỗi class đặt riêng 1 file, cùng 1 gói (package)</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Cách này ở các bài tập có nhiều class, các class cùng 1 loại.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 4:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> Các class cùng là nhân sự của 1 trường học: </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">SinhVien</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">, </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">GiangVienKhoa1</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">,</span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">GiangVienKhoa2</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Với bài này, chúng ta sẽ tạo project với 1 package là truong.hoc, trong</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">package này sẽ có 4 file như sau:</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">File </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">"main.java"</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> chứa hàm main:</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;">package truong</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoc</span><span style="color: #007700;">;<br /><br />public class </span><span style="color: #0000bb;">Main </span><span style="color: #007700;">{<br /><br />    public static </span><span style="color: #0000bb;">void main</span><span style="color: #007700;">(</span><span style="color: #0000bb;">String</span><span style="color: #007700;">[] </span><span style="color: #0000bb;">args</span><span style="color: #007700;">) {<br />        </span><span style="color: #0000bb;">SinhVien a </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">SinhVien</span><span style="color: #007700;">();<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoTen </span><span style="color: #007700;">= </span><span style="color: #dd0000;">"Vũ Văn A"</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">namSinh </span><span style="color: #007700;">= </span><span style="color: #0000bb;">1992</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">toan </span><span style="color: #007700;">= </span><span style="color: #0000bb;">10.0f</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">ly </span><span style="color: #007700;">= </span><span style="color: #0000bb;">9.0f</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoa </span><span style="color: #007700;">= </span><span style="color: #0000bb;">9.5f</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">println</span><span style="color: #007700;">(</span><span style="color: #dd0000;">"Điểm Tb là: " </span><span style="color: #007700;">+ (float) (</span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">toan </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">ly </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoa</span><span style="color: #007700;">) / </span><span style="color: #0000bb;">3</span><span style="color: #007700;">);<br /><br />        </span><span style="color: #0000bb;">GiangVien1 gv1 </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">GiangVien1</span><span style="color: #007700;">();<br />    }<br />}</span></span></code></div></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">File </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">GiangVien.java</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> là 1 class, bạn tạo bằng cách nháy chuột phải vào package chọn New --> Java Class, nội dung như sau:</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;">package truong</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoc</span><span style="color: #007700;">;<br /><br />class </span><span style="color: #0000bb;">SinhVien </span><span style="color: #007700;">{<br /><br />    public </span><span style="color: #0000bb;">String hoTen</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int namSinh</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">float toan</span><span style="color: #007700;">, </span><span style="color: #0000bb;">ly</span><span style="color: #007700;">, </span><span style="color: #0000bb;">hoa</span><span style="color: #007700;">;<br />}</span></span></code></div></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">File GiangVien1.java:</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;">package truong</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoc</span><span style="color: #007700;">;<br /><br />class </span><span style="color: #0000bb;">GiangVien1 </span><span style="color: #007700;">{<br /><br />    public </span><span style="color: #0000bb;">String hoTen</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int namSinh</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">String mon</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int luong</span><span style="color: #007700;">;<br />}</span></span></code></div></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">File </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">GiangVien2.java</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">:</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;">package truong</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoc</span><span style="color: #007700;">;<br /><br />class </span><span style="color: #0000bb;">GiangVien2 </span><span style="color: #007700;">{<br /><br />    public </span><span style="color: #0000bb;">String hoTen</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int namSinh</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">String mon</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int luong</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">String phongThucHanh</span><span style="color: #007700;">;<br />}</span></span></code></div></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Nhờ vào IDE, việc quản lý các class trở lên tiện lợi hơn rất nhiều!</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: red; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"><span style="font-size: medium;">4, Các class được đặt ở nhiều package khác nhau:</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Với những project thực tế, sẽ có rất nhiều class khác nhau được để ở nhiều gói (package) khác nhau.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 4:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> Project này sẽ mở rộng từ các ví dụ trên. Tạo 1 project có tên: QuanLyTruongHoc. Trong project có 3 package: truong.hoc, nhan.su, thu.vien.sach</span><br /><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><br /></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><img alt="Untitled" class="bbCodeImage LbImage" src="http://android.vn/attachments/untitled-png.17645/" style="border: 0px; max-width: 100%;" /></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><br /></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><img alt="Untitled2" class="bbCodeImage LbImage" src="http://android.vn/attachments/untitled2-png.17650/" style="border: 0px; max-width: 100%;" /></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><br /></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><img alt="Untitled3" class="bbCodeImage LbImage" src="http://android.vn/attachments/untitled3-png.17647/" style="border: 0px; max-width: 100%;" /></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Code bài 4 dài tại link: </span><span style="color: #141414; font-family: Roboto, arial, sans-serif;"><span style="font-size: 15px; line-height: 21px;">http://android.vn/attachments/quanlytruonghoc-zip.17653/ </span></span><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">, các bạn Import vào IDE là ok!</span><br /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;">Tham khảo video bên StudyAndShare</div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><br /></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><iframe allowfullscreen="" frameborder="0" height="300" src="http://www.youtube.com/embed/_NveAATqCWY?wmode=opaque" width="500"></iframe></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><br /></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><iframe allowfullscreen="" frameborder="0" height="300" src="http://www.youtube.com/embed/nYAiiRwdzEQ?wmode=opaque" width="500"></iframe></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;">Bài tập về nhà:</span></span><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;"><b><img alt=":D" class="mceSmilieSprite mceSmilie8" src="http://android.vn/styles/default/xenforo/clear.png" style="background-image: url(http://android.vn/styles/default/xenforo/xenforo-smilies-sprite.png); background-position: -20px 0px; background-repeat: no-repeat no-repeat; border: 0px; height: 18px; margin: 0px 1px; vertical-align: text-bottom; width: 18px;" title="Big Grin :D" /></b></span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Đọc hiểu và code lại các ví dụ!</b><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Đọc thêm: </b><a class="internalLink" href="http://android.vn/threads/bai-5-tao-1-doi-tuong-java-dau-tien-cua-ban.23727/" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; color: #009b00; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px -3px; padding: 0px 3px; text-decoration: none;">Tạo 1 đối tượng Java đầu tiên của bạn</a>

Bài 13: Class trong Java (tiếp)

Sau bài viết này, các bạn sẽ có cái nhìn toàn diện hơn về  class  trong 1 project Java (interface, abstract class tương tự), các bạn áp dụng...

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Bài 12: Class (lớp) và đối tượng trong Java!

<span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Để có kiến thức tổng quan và một vài khái niệm mới trong lập trình hướng đối tượng</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Trước tiên, bạn hãy đọc thật kỹ bài này:</span><br /><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><a class="internalLink" href="http://android.vn/threads/bai-4-lap-trinh-huong-doi-tuong-voi-cong-nghe-java.23726/" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; color: #009b00; margin: 0px -3px; padding: 0px 3px; text-decoration: none;">Lập trình hướng đối tượng với công nghệ Java</a></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Rồi xem video anh Việt bên blog StudyAndShare:</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br /><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><iframe allowfullscreen="" frameborder="0" height="300" src="http://www.youtube.com/embed/XskFiP2CSAM?wmode=opaque" width="500"></iframe></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ở bài này, mình sẽ chỉ viết về </span><a class="Tinhte_XenTag_TagLink" href="http://android.vn/tags/class+trong+java/" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; color: #009b00; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px -3px; padding: 0px 3px; text-decoration: none;">class trong Java</a><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> và chúng ta bắt đầu thực hành, làm bài tập nhỏ để làm quen với class.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: red; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"><span style="font-size: medium;">1. Khái niệm class (lớp):</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Chúng ta có thể xem lớp như một khuôn mẫu (template) của đối tượng (Object). Trong đó bao gồm dữ liệu của đối tượng (fields hay properties) và các phương thức (methods) tác động lên thành phần dữ liệu đó gọi là các phương thức của lớp.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Các đối tượng được xây dựng bởi các lớp nên được gọi là các thể hiện của lớp (class instance).</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><a class="Tinhte_XenTag_TagLink" href="http://android.vn/tags/l%E1%BB%9Bp+trong+java/" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; color: #009b00; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px -3px; padding: 0px 3px; text-decoration: none;">Lớp trong java</a><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> gần giống như bản ghi trong lập trình C hoặc pascal, nhưng tất nhiên nó cao cấp hơn.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 1:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> Ta khai báo 1 lớp SinhVien gồm các thuộc tính:</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- hoTen</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- namSinh</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- lopHoc.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Lớp này chính là 1 khuôn mẫu. Khi ta tạo ra các đối tượng dựa trên lớp này, các đối tượng đều tương tự như mẫu trên.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Vd :</b><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Tạo đối tượng a, khi đó a sẽ có 3 thuộc tính, và ta có thể thao tác gán giá trị các thuộc tính đó như sau:</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- hoTen là "Nguyễn Văn A";</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- namSinh là "1992";</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- lopHoc là "At7a";</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">đối tượng b, c, ... cũng tương tự nhưng giá trị của chúng sẽ đặc trưng cho từng đối tượng riêng. Có lẽ, các bạn sẽ thấy nó có vẻ giống với các bản ghi nếu như bạn đã được học lập trình C hoặc Pascal.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;">2. Khai báo/định nghĩa lớp:</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;"></span><span style="color: #007700;">class <</span><span style="color: #0000bb;">ClassName</span><span style="color: #007700;">> {<br />    <</span><span style="color: #0000bb;">kiểu dữ liệu</span><span style="color: #007700;">> <</span><span style="color: #0000bb;">field_1</span><span style="color: #007700;">>;<br />    <</span><span style="color: #0000bb;">kiểu dữ liệu</span><span style="color: #007700;">> <</span><span style="color: #0000bb;">field_2</span><span style="color: #007700;">>;<br />    </span><span style="color: #0000bb;">constructor<br />    method_1<br />    method_2</span><span style="color: #007700;">}</span></span></code></div></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- class: là từ khóa của java</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- ClassName: là tên chúng ta đặt cho lớp</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- field_1, field_2: các thuộc tính, các biến, hay các thành phần dữ liệu của lớp.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- constructor: là sự xây dựng, khởi tạo đối tượng lớp.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- method_1, method_2: là các phương thức/hàm thể hiện các thao tác xử lý, tác động lên các thành phần dữ liệu của lớp.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ở bài này, tạm thời chúng ta sẽ chưa quan tâm tới constructor và method nhé, những bài sau mình sẽ viết rõ về những khái niệm đó.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Các bạn hãy xem vd2 code về lớp để định nghĩa những gì đã viết trong ví dụ 1</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 2:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> (Ở đây, tạm thời chưa cần hiểu public là gì nhé, xuống phần dưới sẽ nói kỹ hơn)</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;"></span><span style="color: #007700;">class </span><span style="color: #0000bb;">SinhVien </span><span style="color: #007700;">{<br />    public </span><span style="color: #0000bb;">String hoTen</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int namSinh</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">String lopHoc</span><span style="color: #007700;">;<br />}</span></span></code></div></div><span style="background-color: white; color: red; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"><span style="font-size: medium;">3. Tạo đối tượng của lớp:</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">ClassName objectName = new ClassName();</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 3:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> Tạo 2 đối tượng sinh viên a và sinh viên b dựa trên class đã định nghĩa ở ví dụ 2:</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;">SinhVien a </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">SinhVien</span><span style="color: #007700;">();</span><span style="color: #0000bb;">SinhVien b </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">SinhVien</span><span style="color: #007700;">();</span></span></code></div></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;">4. Thuộc tính của lớp</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Vùng dữ liệu (fields) hay thuộc tính (properties) của lớp được khai báo bên trong lớp như sau:</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;"></span><span style="color: #007700;">class <</span><span style="color: #0000bb;">ClassName</span><span style="color: #007700;">>{</span><span style="color: #ff8000;">// khai báo những thuộc tính của lớp</span><span style="color: #007700;"><</span><span style="color: #0000bb;">tiền tố</span><span style="color: #007700;">> <</span><span style="color: #0000bb;">kiểu dữ liệu</span><span style="color: #007700;">> </span><span style="color: #0000bb;">field1</span><span style="color: #007700;">;</span><span style="color: #ff8000;">// …</span><span style="color: #007700;">}</span></span></code></div></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Để xác định quyền truy xuất của các đối tượng khác đối với vùng dữ liệu của lớp người ta thường dùng 3 tiền tố sau:</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">public:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> có thể truy xuất từ tất cả các đối tượng khác</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">private:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> một lớp không thể truy xuất vùng private của 1 lớp khác.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">protected:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> vùng protected của 1 lớp chỉ cho phép bản thân lớp đó và những lớp dẫn xuất từ lớp đó truy cập đến.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Xem thêm video Blog StudyAndShare về các thuộc tính này:</b><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br /><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><iframe allowfullscreen="" frameborder="0" height="300" src="http://www.youtube.com/embed/8M9-rEF7t20?wmode=opaque" width="500"></iframe></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 4:</b><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;"></span><span style="color: #007700;">class </span><span style="color: #0000bb;">SinhVien</span><span style="color: #007700;">{<br />    public    </span><span style="color: #0000bb;">String hoTen</span><span style="color: #007700;">;<br />    private    </span><span style="color: #0000bb;">int    namSinh</span><span style="color: #007700;">;<br />    protected </span><span style="color: #0000bb;">String lopHoc</span><span style="color: #007700;">;<br />    public static </span><span style="color: #0000bb;">String tenTruong </span><span style="color: #007700;">= </span><span style="color: #dd0000;">"HV KT Mật Mã"</span><span style="color: #007700;">;<br />}</span></span></code></div></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- Thuộc tính "hoTen" có thể được truy cập đến từ tất cả các đối tượng khác. (public)</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- Thuộc tính "namSinh" chỉ có thể truy cập được từ các đối tượng có kiểu "SinhVien"(private)</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- Thuộc tính "lopHoc", so có thể truy cập được từ các đối tượng có kiểu "SinhVien" và các đối tượng của các lớp con dẫn xuất từ lớp "SinhVien" (protected)</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">- "tenTruong" là biến tĩnh có giá trị là "HV KT Mật Mã"trong tất cả các thể hiện tạo ra từ lớp "SinhVien" (public static)</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Lưu ý:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> Thông thường để an toàn cho vùng dữ liệu của các đối tượng người ta tránh dùng tiền tố public, mà thường chọn tiền tố </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">private</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> để ngăn cản quyền truy cập đến vùng dữ liệu của một lớp từ các phương thức bên ngoài lớp đó.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Vậy class được định nghĩa, được viết ở vị trí nào trong 1 bài lập trình Java hướng đối tượng. Việc tạo đối tượng, truy cập dữ liệu của các đối tượng được tạo tạo những class đó ra sao! Ở bài sau mình sẽ viết rõ và kỹ hơn để các bạn có cái nhìn cụ thể!</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Kết thúc bài này, mình sẽ viết 1 ví dụ đơn giản:</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví Dụ 5:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> Tạo class sinh viên gồm các thuộc tính: hoTen, namSinh, lopHoc</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Tạo 2 đối tượng là sinh viên a và sinh viên b. Gán giá trị cho các thuộc tính và in giá trị các thuộc tính từng sinh viên ra màn hình!</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;">package javademoandroidvn</span><span style="color: #007700;">;</span><span style="color: #ff8000;">//Vd5</span><span style="color: #007700;">class </span><span style="color: #0000bb;">SinhVien </span><span style="color: #007700;">{<br /><br />    public </span><span style="color: #0000bb;">String hoTen</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">int namSinh</span><span style="color: #007700;">;<br />    public </span><span style="color: #0000bb;">String lopHoc</span><span style="color: #007700;">;<br />}<br /><br />public class </span><span style="color: #0000bb;">JavaDemoAndroidVn </span><span style="color: #007700;">{<br /><br />    public static </span><span style="color: #0000bb;">void main</span><span style="color: #007700;">(</span><span style="color: #0000bb;">String</span><span style="color: #007700;">[] </span><span style="color: #0000bb;">args</span><span style="color: #007700;">) {<br /><br />        </span><span style="color: #0000bb;">SinhVien a </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">SinhVien</span><span style="color: #007700;">();<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoTen </span><span style="color: #007700;">= </span><span style="color: #dd0000;">"Vũ Văn Tường"</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">namSinh </span><span style="color: #007700;">= </span><span style="color: #0000bb;">1992</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">lopHoc </span><span style="color: #007700;">= </span><span style="color: #dd0000;">"At7a"</span><span style="color: #007700;">;<br /><br />        </span><span style="color: #0000bb;">SinhVien b </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">SinhVien</span><span style="color: #007700;">();<br />        </span><span style="color: #0000bb;">b</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoTen </span><span style="color: #007700;">= </span><span style="color: #dd0000;">"Nguyễn Văn Tùng"</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">b</span><span style="color: #007700;">.</span><span style="color: #0000bb;">namSinh </span><span style="color: #007700;">= </span><span style="color: #0000bb;">1990</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">b</span><span style="color: #007700;">.</span><span style="color: #0000bb;">lopHoc </span><span style="color: #007700;">= </span><span style="color: #dd0000;">"Bk1"</span><span style="color: #007700;">;<br /><br />        </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">println</span><span style="color: #007700;">(</span><span style="color: #dd0000;">"Thông tin sinh vien a là: "</span><span style="color: #007700;">);<br />        </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">println</span><span style="color: #007700;">(</span><span style="color: #dd0000;">"Họ tên: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoTen </span><span style="color: #007700;">+ </span><span style="color: #dd0000;">" Năm sinh: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">namSinh </span><span style="color: #007700;">+ </span><span style="color: #dd0000;">" Lớp Học: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a</span><span style="color: #007700;">.</span><span style="color: #0000bb;">lopHoc</span><span style="color: #007700;">);<br /><br />        </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">println</span><span style="color: #007700;">(</span><span style="color: #dd0000;">"\nThông tin sinh vien b là: "</span><span style="color: #007700;">);<br />        </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">println</span><span style="color: #007700;">(</span><span style="color: #dd0000;">"Họ tên: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">b</span><span style="color: #007700;">.</span><span style="color: #0000bb;">hoTen </span><span style="color: #007700;">+ </span><span style="color: #dd0000;">" Năm sinh: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">b</span><span style="color: #007700;">.</span><span style="color: #0000bb;">namSinh </span><span style="color: #007700;">+ </span><span style="color: #dd0000;">" Lớp Học: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">b</span><span style="color: #007700;">.</span><span style="color: #0000bb;">lopHoc</span><span style="color: #007700;">);<br />    }<br />}</span></span></code></div></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><span style="color: red;">Tham khảo thêm video bên blog StudyAndShare</span></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><br /></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><iframe allowfullscreen="" frameborder="0" height="300" src="http://www.youtube.com/embed/jkCuNI8U-yM?wmode=opaque" width="500"></iframe></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br /><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><img alt="[IMG]" class="bbCodeImage LbImage" src="http://android.vn/attachments/i-code-java-300x352-1705306-png.16732/" style="border: 0px; max-width: 100%;" /></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;">Bài tập về nhà:</span></span><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;"><b><img alt=":D" class="mceSmilieSprite mceSmilie8" src="http://android.vn/styles/default/xenforo/clear.png" style="background-image: url(http://android.vn/styles/default/xenforo/xenforo-smilies-sprite.png); background-position: -20px 0px; background-repeat: no-repeat no-repeat; border: 0px; height: 18px; margin: 0px 1px; vertical-align: text-bottom; width: 18px;" title="Big Grin :D" /></b></span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; text-decoration: underline;"><b>Bài 1:</b></span><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> </span><span style="background-color: white; color: #ff6600; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Tạo class HocSinh gồm 3 thuộc tính: Họ tên, lớp, điểm trung bình.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #ff6600; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Tạo 2 đối tượng học sinh a và học sinh b, giá trị của các thuộc tính của 2 đối tượng</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #ff6600; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">được nhập từ bàn phím. </span><span style="background-color: white; color: #ff6600; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">So sánh điểm trung bình giữa 2 đối tượng tìm ra người có điểm cao hơn báo ra màn hình console!</span>

Bài 12: Class (lớp) và đối tượng trong Java!

Để có kiến thức tổng quan và một vài khái niệm mới trong lập trình hướng đối tượng Trước tiên, bạn hãy đọc thật kỹ bài này: Lập trình hướng ...

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Bài 11: Thời gian hệ thống trong Java

<span style="background-color: white; color: red; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"><span style="font-size: medium;">1, Tính <a class="Tinhte_XenTag_TagLink" href="http://android.vn/tags/th%E1%BB%9Di+gian/" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; color: #009b00; margin: 0px -3px; padding: 0px 3px; text-decoration: none;">thời gian</a> chạy 1 đoạn lệnh trong chương trình</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">a, Tính thời gian theo mini giây: (10^(-3)s)</b><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Trong đối tượng System có phương thức "currentTimeMillis()", ta dùng nó để đánh dấu 1 mốc thời gian tại</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">vị trí đặt câu lệnh. Để tính thời gian chạy xong 1 đoạn lệnh, ta đặt 2 biến để lấy ra 2 mốc</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">thời gian rồi lấy hiệu của chúng là tính được tổng thời gian chạy chương trình.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ: Chương trình sau sẽ tính thời gian theo mini giây để máy tính sin của 100000 giá trị truyền vào:</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;"></span><span style="color: #007700;">public class </span><span style="color: #0000bb;">JavaDemoAndroidVn </span><span style="color: #007700;">{<br /><br />    public static </span><span style="color: #0000bb;">void main</span><span style="color: #007700;">(</span><span style="color: #0000bb;">String</span><span style="color: #007700;">[] </span><span style="color: #0000bb;">args</span><span style="color: #007700;">) {<br />        </span><span style="color: #ff8000;">//Vd1<br />        </span><span style="color: #0000bb;">long start </span><span style="color: #007700;">= </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">currentTimeMillis</span><span style="color: #007700;">();<br />        for (</span><span style="color: #0000bb;">int i </span><span style="color: #007700;">= </span><span style="color: #0000bb;">1</span><span style="color: #007700;">; </span><span style="color: #0000bb;">i </span><span style="color: #007700;"><= </span><span style="color: #0000bb;">100000</span><span style="color: #007700;">; </span><span style="color: #0000bb;">i</span><span style="color: #007700;">++) {<br />            </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">println</span><span style="color: #007700;">(</span><span style="color: #0000bb;">Math</span><span style="color: #007700;">.</span><span style="color: #0000bb;">sin</span><span style="color: #007700;">(</span><span style="color: #0000bb;">i</span><span style="color: #007700;">));<br />        }<br />        </span><span style="color: #0000bb;">long end </span><span style="color: #007700;">= </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">currentTimeMillis</span><span style="color: #007700;">();<br />        </span><span style="color: #0000bb;">long t </span><span style="color: #007700;">= </span><span style="color: #0000bb;">end </span><span style="color: #007700;">- </span><span style="color: #0000bb;">start</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">println</span><span style="color: #007700;">(</span><span style="color: #dd0000;">"Tổng thời gian: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">t </span><span style="color: #007700;">+ </span><span style="color: #dd0000;">" millisecond"</span><span style="color: #007700;">);<br />    }<br />}</span></span></code></div></div><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">b, Tính thời gian theo nano giây (10^(-9)s)</b><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Tương tự như trên, chỉ khác là ta sẽ dùng phương thức "nanoTime()" trong đối tượng System thay vì</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">dùng phương thức "currentTimeMillis()"</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: red; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"><span style="font-size: medium;">2, Lấy thời gian từ hệ thống</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Bạn xem ví dụ sau, sẽ lấy thời gian từ giờ, phút, giây và ngày, tháng, năm từ hệ thống và hiển thị ra bên ngoài:</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;"></span><span style="color: #007700;">public class </span><span style="color: #0000bb;">JavaDemoAndroidVn </span><span style="color: #007700;">{<br /><br />    public static </span><span style="color: #0000bb;">void main</span><span style="color: #007700;">(</span><span style="color: #0000bb;">String</span><span style="color: #007700;">[] </span><span style="color: #0000bb;">args</span><span style="color: #007700;">) {<br />        </span><span style="color: #ff8000;">//Vd2<br /><br />        //Lay gio he thong<br />        </span><span style="color: #0000bb;">Date thoiGian </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">Date</span><span style="color: #007700;">();<br /><br />        </span><span style="color: #ff8000;">//Khai bao dinh dang ngay thang<br />        </span><span style="color: #0000bb;">SimpleDateFormat dinhDangThoiGian </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">SimpleDateFormat</span><span style="color: #007700;">(</span><span style="color: #dd0000;">"HH:mm:ss dd/MM/yyyy "</span><span style="color: #007700;">);<br /><br />        </span><span style="color: #ff8000;">//parse ngay thang sang dinh dang va chuyen thanh string.<br />        </span><span style="color: #0000bb;">String hienThiThoiGian </span><span style="color: #007700;">= </span><span style="color: #0000bb;">dinhDangThoiGian</span><span style="color: #007700;">.</span><span style="color: #0000bb;">format</span><span style="color: #007700;">(</span><span style="color: #0000bb;">thoiGian</span><span style="color: #007700;">.</span><span style="color: #0000bb;">getTime</span><span style="color: #007700;">());<br /><br />        </span><span style="color: #0000bb;">System</span><span style="color: #007700;">.</span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">println</span><span style="color: #007700;">(</span><span style="color: #dd0000;">"" </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">hienThiThoiGian</span><span style="color: #007700;">);<br />    }<br />}</span></span></code></div></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><span style="color: red;">Các bạn nên tham khảo Video của anh Việt bên Blog StudyAndShare</span></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><br /></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><iframe allowfullscreen="" frameborder="0" height="300" src="http://www.youtube.com/embed/e8x1PON_NBQ?wmode=opaque" width="500"></iframe></div><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><br /></div><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><b><span style="color: red;">Bài tập về nhà:</span></b></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #ff9900; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Các bạn làm lại các ví dụ trên cho thành thạo!</span>

Bài 11: Thời gian hệ thống trong Java

1, Tính  thời gian  chạy 1 đoạn lệnh trong chương trình a, Tính thời gian theo mini giây: (10^(-3)s) Trong đối tượng System có phương thức ...

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Bài 10: Break và Continue trong Java

<br /><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><img alt="images" class="bbCodeImage LbImage" src="http://android.vn/attachments/images-jpg.17542/" style="border: 0px; max-width: 100%;" /></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: red; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"><b><span style="font-size: medium;">1, Lệnh break:</span></b></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Trong cấu trúc switch chúng ta dùng câu lệnh break để thoát thỏi cấu trúc switch trong cùng chứa nó. Tương tự như vậy, trong cấu trúc lặp, câu lệnh break dùng để thoát khỏi cấu trúc lặp trong cùng chứa nó.</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Trong thực tế, đặc biệt là các bài tìm kiếm, sẽ dùng break để thoát vòng lặp khi chúng ta đã tìm thấy kết quả, tránh việc lặp tới tận cùng của vòng lặp, gây lãng phí tài nguyên, vì thế giúp chương trình chạy nhanh hơn!</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br /><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><img alt="break" class="bbCodeImage LbImage" src="http://android.vn/attachments/break-png.17544/" style="border: 0px; max-width: 100%;" /></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 1 : </b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Tìm kiếm số thứ tự của phần tử có giá trị là 10 trong 1 mảng các số nguyên:</span><br /><div class="bbCodeBlock bbCodeQuote bbcmSpoilerBlock" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="attribution type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;"><span class="button JsOnly" style="-webkit-box-shadow: rgb(228, 228, 228) 0px 1px 4px 0px, rgba(204, 204, 204, 0.0980392) 1px 1px 1px inset; background-color: white; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/gradients-sprite.png); background-position: 0px -40px; background-repeat: repeat no-repeat; border-bottom-left-radius: 7px; border-bottom-right-radius: 7px; border-color: rgb(255, 255, 255) rgb(232, 232, 232) rgb(232, 232, 232) rgb(255, 255, 255); border-style: solid; border-top-left-radius: 7px; border-top-right-radius: 7px; border-width: 1px; box-shadow: rgb(228, 228, 228) 0px 1px 4px 0px, rgba(204, 204, 204, 0.0980392) 1px 1px 1px inset; box-sizing: border-box; color: #141414; cursor: pointer; display: inline-block; font-family: Calibri, 'Trebuchet MS', Verdana, Geneva, Arial, Helvetica, sans-serif; font-size: 12px; height: 23px; line-height: 23px; outline: none; padding: 0px 6px; text-align: center;"><span class="bbcm_spoiler_show">Show Spoiler</span></span></div><div class="quotecontent" style="margin: 0px; padding: 0px;"></div></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;">2, Lệnh continue:</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Hiểu đơn giản, chúng ta thường dùng continue để bỏ qua vòng lặp hiện tại khi gặp điều kiện nào đó để tiếp tục sang vòng lặp tiếp theo! Còn bản chất, vì nó cũng là 1 lệnh nhảy, nó nhảy xuống vị trí kết thúc ("}") của khối lệnh trong vòng lặp chứa nó và bỏ qua tất cả các câu lệnh sau nó (Những câu lệnh thuộc cùng khối lệnh với continue của vòng lặp)</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br /><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><img alt="continue" class="bbCodeImage LbImage" src="http://android.vn/attachments/continue-png.17545/" style="border: 0px; max-width: 100%;" /></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 2: </b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Tìm kiếm và in ra số thứ tự và giá trị các phần tử có giá trị nhỏ hơn 35 trong mảng các số nguyên!</span><br /><div class="bbCodeBlock bbCodeQuote bbcmSpoilerBlock" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="attribution type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;"><span class="button JsOnly" style="-webkit-box-shadow: rgb(228, 228, 228) 0px 1px 4px 0px, rgba(204, 204, 204, 0.0980392) 1px 1px 1px inset; background-color: white; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/gradients-sprite.png); background-position: 0px -40px; background-repeat: repeat no-repeat; border-bottom-left-radius: 7px; border-bottom-right-radius: 7px; border-color: rgb(255, 255, 255) rgb(232, 232, 232) rgb(232, 232, 232) rgb(255, 255, 255); border-style: solid; border-top-left-radius: 7px; border-top-right-radius: 7px; border-width: 1px; box-shadow: rgb(228, 228, 228) 0px 1px 4px 0px, rgba(204, 204, 204, 0.0980392) 1px 1px 1px inset; box-sizing: border-box; color: #141414; cursor: pointer; display: inline-block; font-family: Calibri, 'Trebuchet MS', Verdana, Geneva, Arial, Helvetica, sans-serif; font-size: 12px; height: 23px; line-height: 23px; outline: none; padding: 0px 6px; text-align: center;"><span class="bbcm_spoiler_show">Show Spoiler</span></span></div><div class="quotecontent" style="margin: 0px; padding: 0px;"></div></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: red; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"><span style="font-size: medium;">3, Nhãn (label):</span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Không giống như C/C++, Java không hỗ trợ lệnh goto để nhảy đến 1 vị trí nào đó của chương trình. Java dùng kết hợp nhãn (label) với từ khóa break và continue để thay thế cho lệnh</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">goto. Tuy nhiên, ta cũng chỉ có thể sử dụng label đối với các vòng lặp mà thôi!</span><br /><div class="bbCodeBlock bbCodePHP" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;">PHP:</div><div class="code" style="border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; direction: ltr; font-family: Consolas, 'Courier New', Courier, monospace; font-size: 10pt; line-height: 1.24; margin: 0px; max-height: 500px; min-height: 30px; overflow: auto; padding: 10px; white-space: nowrap; word-wrap: normal;"><code style="font-style: inherit; font-weight: inherit; line-height: 13px; margin: 0px; padding: 0px;"><span style="color: black;"><span style="color: #0000bb;">label</span><span style="color: #007700;">:<br />for (</span><span style="color: #0000bb;">…</span><span style="color: #007700;">){<br />    for (</span><span style="color: #0000bb;">…</span><span style="color: #007700;">){<br />    if (<</span><span style="color: #0000bb;">biểu thức điều kiện</span><span style="color: #007700;">>){<br />            break </span><span style="color: #0000bb;">label</span><span style="color: #007700;">;<br />            }<br />        else{<br />            continue </span><span style="color: #0000bb;">label</span><span style="color: #007700;">;<br />        }<br />    }<br />}</span></span></code></div></div><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Lệnh “label:”</b><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Xác định vị trí của nhãn và xem như tên của vòng lặp ngoài. Nếu <biểu thức điều kiện> đúng thì lệnh break label sẽ thực hiện việc nhảy ra khỏi vòng lặp có nhãn là “label”, ngược lại sẽ tiếp tục vòng lặp có nhãn “label” (khác với break và continue thông thường chỉ thoát khỏi hay tiếp tục vòng lặp trong cùng chứa nó).</span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Ví dụ 3: </b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Bài sau đây nhập xuất ma trận, tìm kiếm chỉ số của phần tử tìm thấy đầu tiên theo yêu cầu!</span><br /><div class="bbCodeBlock bbCodeQuote bbcmSpoilerBlock" style="background-color: white; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; border-top-left-radius: 5px; border-top-right-radius: 5px; border: 1px solid rgb(228, 228, 228); color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 1em 0px; padding: 0px; position: relative;"><div class="attribution type" style="background-color: #009b00; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/category-23px-light.png); background-position: 50% 0%; background-repeat: repeat no-repeat; border-bottom-color: rgb(228, 228, 228); border-bottom-style: solid; border-bottom-width: 1px; border-top-left-radius: 4px; border-top-right-radius: 4px; color: white; font-size: 11px; margin: 0px; padding: 3px 8px;"><span class="button JsOnly" style="-webkit-box-shadow: rgb(228, 228, 228) 0px 1px 4px 0px, rgba(204, 204, 204, 0.0980392) 1px 1px 1px inset; background-color: white; background-image: url(http://android.vn/styles/soft_responsive_green/xenforo/gradients/gradients-sprite.png); background-position: 0px -40px; background-repeat: repeat no-repeat; border-bottom-left-radius: 7px; border-bottom-right-radius: 7px; border-color: rgb(255, 255, 255) rgb(232, 232, 232) rgb(232, 232, 232) rgb(255, 255, 255); border-style: solid; border-top-left-radius: 7px; border-top-right-radius: 7px; border-width: 1px; box-shadow: rgb(228, 228, 228) 0px 1px 4px 0px, rgba(204, 204, 204, 0.0980392) 1px 1px 1px inset; box-sizing: border-box; color: #141414; cursor: pointer; display: inline-block; font-family: Calibri, 'Trebuchet MS', Verdana, Geneva, Arial, Helvetica, sans-serif; font-size: 12px; height: 23px; line-height: 23px; outline: none; padding: 0px 6px; text-align: center;"><span class="bbcm_spoiler_show">Show Spoiler</span></span></div><div class="quotecontent" style="margin: 0px; padding: 0px;"></div></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;">Bài tập về nhà:</span></span><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;"><b><img alt=":D" class="mceSmilieSprite mceSmilie8" src="http://android.vn/styles/default/xenforo/clear.png" style="background-image: url(http://android.vn/styles/default/xenforo/xenforo-smilies-sprite.png); background-position: -20px 0px; background-repeat: no-repeat no-repeat; border: 0px; height: 18px; margin: 0px 1px; vertical-align: text-bottom; width: 18px;" title="Big Grin :D" /></b></span></span><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><br /><div align="center" style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px; margin: 0px; padding: 0px;"><span style="color: #ff9900;"><span style="font-family: 'Times New Roman';"><b><img alt="[IMG]" class="bbCodeImage LbImage" src="http://android.vn/attachments/16732/" style="border: 0px; max-width: 100%;" /></b></span></span></div><br style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;" /><span style="background-color: white; color: #ff6600; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"><span style="font-size: small;"><span style="color: black;"><span style="text-decoration: underline;"><b>Bài 1:</b></span><span style="color: #ff6600;"> Nhập 1 danh sách họ tên sinh viên 1 lớp học vào 1 mảng n phần tử. Sắp xếp theo thứ tự a, b, c ... rồi dùng thuật toán tìm kiếm nhị phân, tìm kiếm chính xác tên sinh viên vừa nhập và in ra màn hình số thứ tự của sinh viên đó!</span></span></span></span>

Bài 10: Break và Continue trong Java

1, Lệnh break: Trong cấu trúc switch chúng ta dùng câu lệnh break để thoát thỏi cấu trúc switch trong cùng chứa nó. Tương tự như vậy, trong ...

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