Bài 22: Try, catch, finally 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="20111020_Java-Xulyngoaile-p2_2" class="bbCodeImage LbImage" src="http://android.vn/attachments/20111020_java-xulyngoaile-p2_2-gif.18105/" 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><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Trước khi vào chi tiết, mình sẽ nêu 1 tình huống như này, đó là lỗi chia cho 0.</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;">Bình thường theo các bài trước, các bạn sẽ dùng if, else để loại bỏ, in ra lỗi. (tất nhiên nếu bạn đã biết try catch rồi thì không nói </span><img alt=":D" class="mceSmilieSprite mceSmilie8" src="http://android.vn/styles/default/xenforo/clear.png" style="background-color: white; 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; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; height: 18px; line-height: 21px; margin: 0px 1px; vertical-align: text-bottom; width: 18px;" title="Big Grin :D" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">). Đọc xong bài này, các bạn sẽ có thêm 1 cách khác, và tất nhiên nó còn sử dụng để bắt và xử lý nhiều loại lỗi hơn!</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:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> Các bạn xem đoạn code này trước khi đọc lý thuyết, chạy thử nó, có thể nó cũng khá dễ hiểu!</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 javaandroidvn</span><span style="color: #007700;">;<br /><br />public class </span><span style="color: #0000bb;">JavaAndroidVn </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;">int a </span><span style="color: #007700;">= </span><span style="color: #0000bb;">5</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">int b </span><span style="color: #007700;">= </span><span style="color: #0000bb;">0</span><span style="color: #007700;">;<br /><br />        </span><span style="color: #ff8000;">//Cách các bài trước thường làm, dùng if, else:<br />        </span><span style="color: #007700;">if (</span><span style="color: #0000bb;">b </span><span style="color: #007700;">== </span><span style="color: #0000bb;">0</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;">"Lỗi chia cho 0"</span><span style="color: #007700;">);<br />        } else {<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;">"a/b = " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a </span><span style="color: #007700;">/ </span><span style="color: #0000bb;">b</span><span style="color: #007700;">);<br />        }<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;">"\nCách dùng try - catch - finally \n"</span><span style="color: #007700;">);<br /><br />        </span><span style="color: #ff8000;">//Sử dụng try, catch để bắt lỗi:<br />        </span><span style="color: #007700;">try {<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;">"a/b = " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a </span><span style="color: #007700;">/ </span><span style="color: #0000bb;">b</span><span style="color: #007700;">);<br />        } catch (</span><span style="color: #0000bb;">Exception e1</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;">"Có lỗi gì đó xảy ra  "</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;">"Tên lỗi là: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">e1</span><span style="color: #007700;">);<br />        } </span><span style="color: #0000bb;">finally </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;">"Có lỗi hay không thì cái dòng cuối cùng này vẫn được in ra!"</span><span style="color: #007700;">);<br />        }<br /><br />    }<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;">1, Try - catch:</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;">- Trong ví dụ trên, trong khối</span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> try{}</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> là những dòng lệnh chúng ta cần thực hiện!</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;">Khối </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">catch (Exception e1) {}</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> là nơi chứa các dòng lệnh thực hiện khi phát hiện lỗi!</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;">- Ở đây, ta cần hiểu rõ khái niệm </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Exception:</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;">Exception</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> (Ngoại lệ) là sự kiện xảy ra khi một chương trình đang chạy mà phát sinh ra lỗi. Nó sẽ làm gián đoạn chương trình!</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;">(Exception e1)</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> trong đó </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">"e1"</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> là tên của được gán nếu đối tượng bị lỗi, các bạn có thể đặt tên này bằng các từ 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;">- Bạn có thể in </span><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">"e1"</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> ra ngoài, sẽ thấy được lỗi cụ thể!</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;"> Exception</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> là lớp cha, nó nói chung, và in ra các lỗi, ngoài ra còn có lớp con cụ thể và các ngoại lệ khác 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;">Exception | Lớp nền của run-time</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;">NullPointerException | Một đối tượng không tồn 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;">ClassNotFoundException | Không tìm thấy Class</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;">FileNotFoundException | Không tìm thấy file</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;">SecurityException | Exception liên quan đến bảo mật</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;">ArrayIndexOutOfBoundsException | Vượt quá chỉ mục của mảng</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;">IllegalAccessException | Truy cập không hợp lệ</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;">IllegalArgumentException | Đối số hàm</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;">ArithmeticException | Lỗi thực thi một phép toán</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;">NumberFormatException | Định dạng số không đúng</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;">IOException | Lỗi nhập xuất</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;">EOFException | Kết thúc một tập tin</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;">NoSuchMethodException | Sai tên phương thức</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;">InterruptedException | Ngắt luồng đang được thực thi</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:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> In ra lỗi cụ thể vượt quá chỉ mục của mảng.</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 javaandroidvn</span><span style="color: #007700;">;<br /><br />public class </span><span style="color: #0000bb;">JavaAndroidVn </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;">int arrInt</span><span style="color: #007700;">[] = {</span><span style="color: #0000bb;">1</span><span style="color: #007700;">, </span><span style="color: #0000bb;">2</span><span style="color: #007700;">, </span><span style="color: #0000bb;">4</span><span style="color: #007700;">, </span><span style="color: #0000bb;">7</span><span style="color: #007700;">, </span><span style="color: #0000bb;">10</span><span style="color: #007700;">};<br />        try {<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;">"arrInt[6] = " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">arrInt</span><span style="color: #007700;">[</span><span style="color: #0000bb;">6</span><span style="color: #007700;">]);<br /><br />        } catch (</span><span style="color: #0000bb;">ArrayIndexOutOfBoundsException e2</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;">"Lỗi! Vượt quá chỉ mục của mảng! " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">e2</span><span style="color: #007700;">);<br />        }<br /><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;">Ngoài ra, để in nhiều Exception thì ra làm 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;"></span><span style="color: #007700;">try {<br />    </span><span style="color: #ff8000;">//Nội dung muốn bẫy lỗi</span><span style="color: #007700;">} catch (</span><span style="color: #0000bb;">ExceptionType1 e</span><span style="color: #007700;">) {<br />    </span><span style="color: #ff8000;">//Khối lệnh cho lỗi</span><span style="color: #007700;">}catch (</span><span style="color: #0000bb;">ExceptionType2 e1</span><span style="color: #007700;">) {<br />    </span><span style="color: #ff8000;">//Khối lệnh cho lỗi</span><span style="color: #007700;">} catch (</span><span style="color: #0000bb;">Exception ex</span><span style="color: #007700;">) {<br />    </span><span style="color: #ff8000;">//Exception cho những cái còn lại</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;">Trong đó ExceptionType là những loại Exception cụ thể đã nêu ở phía 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, Finally?</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;">Nó nằm ở cuối cùng của khối lệnh try - catch - finally, nó luôn luôn được thực hiện ngay cả khi chương trình có bắt được lỗi</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;">hay không!</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 khối lệnh đầy đủ như ví dụ ở đầu bài, dòng System.out.println("Có lỗi hay không thì cái dòng cuối cùng này vẫn được in ra!");</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;">Luôn luôn được thực hiện và in ra khi bạn gán bất giá trị nào cho 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;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Xem thêm video nói khá đầy đủ về try - catch - finally của Blog StudyAndShare</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/VJYBBXhb5tY?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/UpG2gzPwGe4?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;">Bổ sung thêm video về throw and throws</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;"><b><iframe allowfullscreen="" frameborder="0" height="300" src="http://www.youtube.com/embed/KQV7-acf44Q?wmode=opaque" width="500"></iframe></b></div><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;"><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;" /><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Làm lại bài giải phương trình ax + b = 0 . Lập trình hướng đối tượng. Các hệ số nhập vào từ bàn phím. Sử dụng try - catch để bẫy các lỗi khi nhập sai kiểu dữ liệu, ví dụ nhập số lại nhập chữ. Bẫy lỗi chia cho 0.</span>

Bài 22: Try, catch, finally trong Java

Trước khi vào chi tiết, mình sẽ nêu 1 tình huống như này, đó là lỗi chia cho 0. Bình thường theo các bài trước, các bạn sẽ dùng if, else để ...

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Bài 21: Final class, abstract class và interface trong Java

<span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: medium;"><span style="color: red;">1, <a class="Tinhte_XenTag_TagLink" href="http://android.vn/tags/final+class/" 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;">Final class</a> (<a class="Tinhte_XenTag_TagLink" href="http://android.vn/tags/l%E1%BB%9Bp+v%C3%B4+sinh/" 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;">Lớp vô sinh</a>):</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;">Lớp không thể có lớp dẫn xuất từ nó (không có lớp con) gọi là lớp “vô sinh”, hay nói cách khác không thể kế thừa được từ một lớp “vô sinh”. Lớp “vô sinh” dùng để hạn chế, ngăn ngừa các lớp khác dẫn xuất từ 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;">Để khai báo một lớp là lớp “vô sinh”, chúng ta dùng từ khóa final class.</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;">Tất cả các phương thức của lớp vô sinh đều vô sinh, nhưng các thuộc tính của lớp vô sinh thì có thể không vô sinh.</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;">- Xem thêm video 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/1tm9pxzl-Eo?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:</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;">public final class </span><span style="color: #0000bb;">A </span><span style="color: #007700;">{<br />    public final </span><span style="color: #0000bb;">int x</span><span style="color: #007700;">;<br />    private </span><span style="color: #0000bb;">int y</span><span style="color: #007700;">;<br />    public final </span><span style="color: #0000bb;">void method_1</span><span style="color: #007700;">(){<br />    </span><span style="color: #ff8000;">// …<br />    </span><span style="color: #007700;">}<br />    public final </span><span style="color: #0000bb;">void method_2</span><span style="color: #007700;">(){<br />    </span><span style="color: #ff8000;">// …<br />    </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: medium;"><span style="color: red;">2, <a class="Tinhte_XenTag_TagLink" href="http://android.vn/tags/abstract+class/" 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;">Abstract class</a> (<a class="Tinhte_XenTag_TagLink" href="http://android.vn/tags/l%E1%BB%9Bp+tr%E1%BB%ABu+t%C6%B0%E1%BB%A3ng/" 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;">Lớp trừu tượng</a>):</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;">Một lớp trừu tượng thì không có thể hiện nghĩa là ta không thể khởi tạo nó bằng toán tử new, và một phương thức trong nó là abstract thì chỉ được đưa ra định nghĩa (khai báo) mà không được thực thi và nó sẽ được override lại trong các lớp con kế thừa. Và trong lớp mà tồn tại phương thức abstract thì lớp đó cũng được định nghĩa abstract.</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;">- Lớp trừu tượng là lớp không có khai báo các thuộc tính thành phần và các phương thức.</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;">- Bất cứ class nào kết thừa abstract class nào đó phải định nghĩa lại các abstract mothods của lớp mà nó thừa kế hoặc không định nghĩa lại nhưng phải ghi lại abstract mothods đó.</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;">- Abstract class là class có chứa các abstract mothods</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 methods trong abstract class phải khai báo với từ khóa abstract (không giống như </span><a class="Tinhte_XenTag_TagLink" href="http://android.vn/tags/interface/" 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;">interface</a><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> vì interface mặc định gán abstract cho các mothods)</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;">- Một abstract class có thể chứa cả abstract mothods và các mothods thường.</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;">- Khi một class có chứa abstract mothod thì bắt buộc phải có từ khóa abstract đằng trước tên class đó.</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;">abstract class </span><span style="color: #0000bb;">A</span><span style="color: #007700;">{<br />    abstract </span><span style="color: #0000bb;">void method_1</span><span style="color: #007700;">();<br />}<br />public class </span><span style="color: #0000bb;">B </span><span style="color: #007700;">extends </span><span style="color: #0000bb;">A</span><span style="color: #007700;">{<br />    @</span><span style="color: #0000bb;">Override<br />    </span><span style="color: #007700;">public </span><span style="color: #0000bb;">void method_1</span><span style="color: #007700;">(){<br />    </span><span style="color: #ff8000;">// cài đặt chi tiết cho phương thức method_1<br />    // trong lớp con B.<br />    // …<br />    </span><span style="color: #007700;">}<br />}<br />public class </span><span style="color: #0000bb;">C </span><span style="color: #007700;">extends </span><span style="color: #0000bb;">A</span><span style="color: #007700;">{<br />    @</span><span style="color: #0000bb;">Override<br />    </span><span style="color: #007700;">public </span><span style="color: #0000bb;">void method_1</span><span style="color: #007700;">(){<br />    </span><span style="color: #ff8000;">// cài đặt chi tiết cho phương thức method_1<br />    // trong lớp con C.<br />    // …<br />    </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;">Lưu ý:</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 phương thức được khai báo dùng các tiền tố private và static thì không được khai báo là trừu tượng abstract. Tiền tố private thì không thể truy xuất từ các lớp dẫn xuất, còn tiền tố static thì chỉ dùng riêng cho lớp khai báo mà thôi.</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;">* Phương thức trong abstract class có 2 cách để khai báo:</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;">- Khai báo bình thường như class</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;">- Khai báo giống như interface nhưng phải có thêm từ khóa abstract</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;">Code demo:</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;">package java</span><span style="color: #007700;">.</span><span style="color: #0000bb;">demo</span><span style="color: #007700;">.</span><span style="color: #0000bb;">android</span><span style="color: #007700;">.</span><span style="color: #0000bb;">vn</span><span style="color: #007700;">;<br /><br />abstract class </span><span style="color: #0000bb;">nhanSu </span><span style="color: #007700;">{<br /><br />    abstract </span><span style="color: #0000bb;">void show</span><span style="color: #007700;">();<br />}<br /><br />class </span><span style="color: #0000bb;">hocSinh </span><span style="color: #007700;">extends </span><span style="color: #0000bb;">nhanSu </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 /><br />    public </span><span style="color: #0000bb;">void show</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;">"Hello " </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;">namSinh</span><span style="color: #007700;">);<br />    }<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 />        </span><span style="color: #0000bb;">hocSinh a </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">hocSinh</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;">show</span><span style="color: #007700;">();<br /><br />    }<br />}</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;">3, Interface (Khác với GUI - Nó không phải là giao diện người dùng)</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;">- Như chúng ta đã biết một lớp trong java chỉ có một siêu lớp (super class) trực tiếp hay một cha duy nhất (đơn thừa kế). Để tránh đi tính phức tạp của đa thừa kế (multi-inheritance) trong lập trình hướng đối tượng, Java thay thế bằng interface. Một lớp có thể kế thừa từ nhiều interface với các lớp khác để thừa hưởng thêm vùng dữ liệu và phương thức của các interface này.</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;">- Interface được khai báo như một lớp. Nhưng các thuộc tính của interface là các hằng (khai báo dùng từ khóa final) và các phương thức của interface là trừu tượng (mặc dù không có từ</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;">khóa abstract).</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;">- Mothods trừu tượng là các mothods chỉ có phần header, không có phần body.(Xem ví dụ phía dưới)</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 các lớp có cài đặt các interface ta phải tiến hành cài đặt cụ thể các phương thức này.</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;">- Interface được định nghĩa nhằm làm cho code rành mạch hơn vì các class có thể implements các interface.</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: </b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Code ví dụ của video 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/jkCuNI8U-yM?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/29RvYx4P8HU?wmode=opaque" width="500"></iframe></div><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;">DemoJavaBasic </span><span style="color: #007700;">{<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;">Manager mana </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">Manager</span><span style="color: #007700;">();<br />            </span><span style="color: #0000bb;">mana</span><span style="color: #007700;">.</span><span style="color: #0000bb;">show</span><span style="color: #007700;">();<br />      }<br />}<br />interface </span><span style="color: #0000bb;">Human</span><span style="color: #007700;">{<br />      public static final </span><span style="color: #0000bb;">int AVG_AGE </span><span style="color: #007700;">= </span><span style="color: #0000bb;">100</span><span style="color: #007700;">;<br />      </span><span style="color: #0000bb;">int AVG_WEIGHT </span><span style="color: #007700;">= </span><span style="color: #0000bb;">60</span><span style="color: #007700;">;<br /><br />      public abstract </span><span style="color: #0000bb;">void show</span><span style="color: #007700;">();<br />      </span><span style="color: #0000bb;">void study</span><span style="color: #007700;">();<br />}<br />class </span><span style="color: #0000bb;">Manager </span><span style="color: #007700;">implements </span><span style="color: #0000bb;">Human</span><span style="color: #007700;">{<br /><br />      @</span><span style="color: #0000bb;">Override<br />      </span><span style="color: #007700;">public </span><span style="color: #0000bb;">void show</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;">"Tuoi trung bình: "</span><span style="color: #007700;">+ </span><span style="color: #0000bb;">AVG_AGE</span><span style="color: #007700;">);<br /><br />      }<br /><br />      @</span><span style="color: #0000bb;">Override<br />      </span><span style="color: #007700;">public </span><span style="color: #0000bb;">void study</span><span style="color: #007700;">() {<br />            </span><span style="color: #ff8000;">// TODO Auto-generated method stub<br /><br />      </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;">Có một vấn đề khác với lớp là một giao diện (interface) không chỉ có một giao diện cha trực tiếp mà có thể dẫn xuất cùng lúc nhiều giao diện khác (hay có nhiều giao diện cha). Khi đó nó sẽ kế thừa tất cả các giá trị hằng và các phương thức của các giao diện cha. Các giao diện cha được liệt kê thành chuỗi và cách nhau bởi dấu phẩy “,”. Khai báo 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;"></span><span style="color: #007700;">public interface </span><span style="color: #0000bb;">InterfaceName </span><span style="color: #007700;">extends </span><span style="color: #0000bb;">interface1</span><span style="color: #007700;">, </span><span style="color: #0000bb;">interface2</span><span style="color: #007700;">,</span><span style="color: #0000bb;">interface3</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;">Ví dụ:</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;">interface </span><span style="color: #0000bb;">DienTich </span><span style="color: #007700;">{<br /><br />    public abstract </span><span style="color: #0000bb;">void sHinhVuong</span><span style="color: #007700;">(</span><span style="color: #0000bb;">float a</span><span style="color: #007700;">);<br /><br />    public abstract </span><span style="color: #0000bb;">void sHinhChuNhat</span><span style="color: #007700;">(</span><span style="color: #0000bb;">float a</span><span style="color: #007700;">, </span><span style="color: #0000bb;">float b</span><span style="color: #007700;">);<br />}<br /><br />interface </span><span style="color: #0000bb;">ChuVi </span><span style="color: #007700;">{<br /><br />    public abstract </span><span style="color: #0000bb;">void cVHinhVuong</span><span style="color: #007700;">(</span><span style="color: #0000bb;">float a</span><span style="color: #007700;">);<br /><br />    public abstract </span><span style="color: #0000bb;">void cVHinhChuNhat</span><span style="color: #007700;">(</span><span style="color: #0000bb;">float a</span><span style="color: #007700;">, </span><span style="color: #0000bb;">float b</span><span style="color: #007700;">);<br />}<br /><br />interface </span><span style="color: #0000bb;">CongThuc </span><span style="color: #007700;">extends </span><span style="color: #0000bb;">DienTich</span><span style="color: #007700;">, </span><span style="color: #0000bb;">ChuVi </span><span style="color: #007700;">{<br />}<br /><br />class </span><span style="color: #0000bb;">CongThucTinh </span><span style="color: #007700;">implements </span><span style="color: #0000bb;">CongThuc </span><span style="color: #007700;">{</span><span style="color: #ff8000;">//Hoặc viết là class CongThucTinh implements DienTich,ChuVi cũng được!<br /><br />    </span><span style="color: #007700;">@</span><span style="color: #0000bb;">Override<br />    </span><span style="color: #007700;">public </span><span style="color: #0000bb;">void sHinhVuong</span><span style="color: #007700;">(</span><span style="color: #0000bb;">float a</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;">"Diện tích hình vuông là: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a </span><span style="color: #007700;">* </span><span style="color: #0000bb;">a</span><span style="color: #007700;">);<br />    }<br /><br />    @</span><span style="color: #0000bb;">Override<br />    </span><span style="color: #007700;">public </span><span style="color: #0000bb;">void sHinhChuNhat</span><span style="color: #007700;">(</span><span style="color: #0000bb;">float a</span><span style="color: #007700;">, </span><span style="color: #0000bb;">float b</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;">"Diện tích hình chữ nhật là: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">a </span><span style="color: #007700;">* </span><span style="color: #0000bb;">b</span><span style="color: #007700;">);<br />    }<br /><br />    @</span><span style="color: #0000bb;">Override<br />    </span><span style="color: #007700;">public </span><span style="color: #0000bb;">void cVHinhVuong</span><span style="color: #007700;">(</span><span style="color: #0000bb;">float a</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;">"Chu vi hình vuông là: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">4 </span><span style="color: #007700;">* </span><span style="color: #0000bb;">a</span><span style="color: #007700;">);<br />    }<br /><br />    @</span><span style="color: #0000bb;">Override<br />    </span><span style="color: #007700;">public </span><span style="color: #0000bb;">void cVHinhChuNhat</span><span style="color: #007700;">(</span><span style="color: #0000bb;">float a</span><span style="color: #007700;">, </span><span style="color: #0000bb;">float b</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;">"Chu vi hình chữ nhật là: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">2 </span><span style="color: #007700;">* (</span><span style="color: #0000bb;">a </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">b</span><span style="color: #007700;">));<br />    }<br />}<br /><br />public class </span><span style="color: #0000bb;">JavaAndroidVn </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;">CongThucTinh x </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">CongThucTinh</span><span style="color: #007700;">();<br />        </span><span style="color: #0000bb;">x</span><span style="color: #007700;">.</span><span style="color: #0000bb;">sHinhVuong</span><span style="color: #007700;">(</span><span style="color: #0000bb;">5.0f</span><span style="color: #007700;">);<br />        </span><span style="color: #0000bb;">x</span><span style="color: #007700;">.</span><span style="color: #0000bb;">cVHinhVuong</span><span style="color: #007700;">(</span><span style="color: #0000bb;">5.0f</span><span style="color: #007700;">);<br />        </span><span style="color: #0000bb;">x</span><span style="color: #007700;">.</span><span style="color: #0000bb;">sHinhChuNhat</span><span style="color: #007700;">(</span><span style="color: #0000bb;">5.5f</span><span style="color: #007700;">, </span><span style="color: #0000bb;">10.0f</span><span style="color: #007700;">);<br />        </span><span style="color: #0000bb;">x</span><span style="color: #007700;">.</span><span style="color: #0000bb;">cVHinhChuNhat</span><span style="color: #007700;">(</span><span style="color: #0000bb;">5.5f</span><span style="color: #007700;">, </span><span style="color: #0000bb;">10.0f</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;">Đọc thêm về Interface:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> </span><a class="internalLink" href="http://android.vn/threads/cac-interface-giao-dien-be-mat-trong-lap-trinh-java.23904/" 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;">Các interface (giao diện, bề mặt) trong lập trình Java</a><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;">4, So sánh abstract class và interface:</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;" /><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;"><b><span style="font-size: medium;"><span style="color: red;"><img alt="abstractandinterface" class="bbCodeImage LbImage" src="http://android.vn/attachments/abstractandinterface-jpg.18107/" style="border: 0px; max-width: 100%;" /></span></span></b></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: 15px; line-height: 21px;">Mấy đoạn này là mình sưu tầm trên mạng nhé:</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;">- Một class chỉ có thể kế thừa từ một abstract class, nhưng có thể kế thừa nhiều interface.</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 Interface chỉ có thể khai báo các fields, methods, mà không được hiện thực nó. Còn đối với abstract thì dùng các biến, hiện thực cách methods.</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 fields, methods trong interace đều là public và bắt buộc các class kế thừa phải cài đặt nó (abstract). Trong abstract class thì có các fields, methods có thể là private, internal, public, protected và có thể là abstract hoặc non-abstract.</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;">- Interface dùng để gom các hành động cần được hiện thực, các khả năng của một đối tượng, còn abstract class cho các lớp thừa kế cùng 1 loại, tính chất hay trạng thái.</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;">- Abstract class có tốc độ thực thi nhanh hơn interface.</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;">- Thêm 1 tính năng mới vào interface sẽ phá vỡ toàn bộ các lớp hiện thực, còn abstract thì không.</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 về interface, các thành viên của interface phải được thực thi trong các lớp mà kế thừa từ 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;">- Nhìn một cách nào đó, bạn có thể thấy rằng, Interface giống như những câu lạc bộ, và Abstract class là một ông bố trong gia đình.</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;">Một câu lạc bộ luôn luôn có một bộ quy tắc hay nôi qui mà mọi thành viên luôn phải tuân theo.</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;">Một ông bố trong gia đình thì khác, ông có tài sản mà con cháu có thể kế thừa, ông cũng có những qui định trong di chúc – ai là người được kế thừa tài sản của ông! Bạn có thể tham gia cùng lúc nhiều câu lạc bộ như việc một Class "kế thừa" (Implement) nhiều Interface.</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;">Một khi đã tham gia vào CLB nào, bạn phải tuân thủ tất cả các qui tắc của CLB đó, không quan tâm bạn là thành viên của bao nhiêu CLB. Đó là việc tại sao phải Implement đầy đủ các Interface member.</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;">CLB không để lại tài sản cho các bạn, nhưng bố của bạn thì có, ông ấy cho bạn tài sản (không nếu ông ấy không thích Laughing) và cũng bắt bạn tuân theo các qui tắc – gia qui. Và một khi đã là con của người này thì bạn không thể nào là con của người khác giống như không thể kế thừa từ nhiều Abstract 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;" /><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" /> <span style="font-size: 15px;"><span style="color: #141414;">Làm lại thành thạo các ví dụ trên!</span></span></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;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Đọc thêm:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> </span><a class="internalLink" href="http://android.vn/threads/cac-interface-giao-dien-be-mat-trong-lap-trinh-java.23904/" 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;">Các interface (giao diện, bề mặt) trong lập trình Java</a>

Bài 21: Final class, abstract class và interface trong Java

1,  Final class  ( Lớp vô sinh ): Lớp không thể có lớp dẫn xuất từ nó (không có lớp con) gọi là lớp “vô sinh”, hay nói cách khác không thể k...

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Bài 20: Inner class 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="Untitled" class="bbCodeImage LbImage" src="http://android.vn/attachments/untitled-png.17941/" 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><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:</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;">Một class nằm trong class khác được gọi là </span><a class="Tinhte_XenTag_TagLink" href="http://android.vn/tags/inner+class/" 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;">inner class</a><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">. Inner class có thể coi như một thuộc tính của class. Nghĩa là bạn không thể khởi tạo đối tượng B nếu chưa khởi tạo đối tượng A.</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;">A</span><span style="color: #007700;">{<br />    class </span><span style="color: #0000bb;">B</span><span style="color: #007700;">{<br />    }<br />}</span></span></code></div></div><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;">A obj1 </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">A</span><span style="color: #007700;">();</span><span style="color: #0000bb;">A</span><span style="color: #007700;">.</span><span style="color: #0000bb;">B obj2 </span><span style="color: #007700;">= </span><span style="color: #0000bb;">obj1</span><span style="color: #007700;">.new </span><span style="color: #0000bb;">B</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;">Bởi class B nằm trong class A nên nó có thể truy cập tất cả các thuộc tính hay phương thức của class A</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;">A  </span><span style="color: #007700;">{<br />    private </span><span style="color: #0000bb;">int x </span><span style="color: #007700;">= </span><span style="color: #0000bb;">8</span><span style="color: #007700;">;<br />    class </span><span style="color: #0000bb;">B </span><span style="color: #007700;">{<br />        public </span><span style="color: #0000bb;">void printInt</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;">x</span><span style="color: #007700;">);<br />        }<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;">Để sử dụng method vừa tạo, ta có thể viết:</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;">obj2.printInt();</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, Một số ví dụ:</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;">Ví dụ 1:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> Ví dụ 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/D9e4UwKqvSg?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 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;">DemoJavaAndroidVn </span><span style="color: #007700;">{<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;">Outer out </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">Outer</span><span style="color: #007700;">();<br />            </span><span style="color: #0000bb;">out</span><span style="color: #007700;">.</span><span style="color: #0000bb;">show</span><span style="color: #007700;">();<br />      }<br />}<br /><br />class </span><span style="color: #0000bb;">Outer </span><span style="color: #007700;">{<br />      public </span><span style="color: #0000bb;">void show</span><span style="color: #007700;">() {<br />            </span><span style="color: #0000bb;">Inner in </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">Inner</span><span style="color: #007700;">();<br />            </span><span style="color: #0000bb;">in</span><span style="color: #007700;">.</span><span style="color: #0000bb;">display</span><span style="color: #007700;">();<br />      }<br /><br />      class </span><span style="color: #0000bb;">Inner </span><span style="color: #007700;">{<br />            public </span><span style="color: #0000bb;">void display</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;">"Đây là inner class."</span><span style="color: #007700;">);<br />            }<br />      }<br />}<br /><br />class </span><span style="color: #0000bb;">B </span><span style="color: #007700;">{<br />      public </span><span style="color: #0000bb;">void show</span><span style="color: #007700;">() {<br />            </span><span style="color: #0000bb;">Outer</span><span style="color: #007700;">.</span><span style="color: #0000bb;">Inner in </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">Outer</span><span style="color: #007700;">().new </span><span style="color: #0000bb;">Inner</span><span style="color: #007700;">();<br />            </span><span style="color: #0000bb;">in</span><span style="color: #007700;">.</span><span style="color: #0000bb;">display</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;">Ví dụ 2:</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;">package javaandroidvn</span><span style="color: #007700;">;<br /><br />class </span><span style="color: #0000bb;">ThoiGian </span><span style="color: #007700;">{<br /><br />    public </span><span style="color: #0000bb;">int ngay</span><span style="color: #007700;">, </span><span style="color: #0000bb;">thang</span><span style="color: #007700;">, </span><span style="color: #0000bb;">nam</span><span style="color: #007700;">;<br /><br />    class </span><span style="color: #0000bb;">Time </span><span style="color: #007700;">{<br /><br />        public </span><span style="color: #0000bb;">int gio</span><span style="color: #007700;">, </span><span style="color: #0000bb;">phut</span><span style="color: #007700;">, </span><span style="color: #0000bb;">giay</span><span style="color: #007700;">;<br /><br />        public </span><span style="color: #0000bb;">void showTime</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;">"Ngày " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">ngay </span><span style="color: #007700;">+ </span><span style="color: #dd0000;">"/" </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">thang </span><span style="color: #007700;">+ </span><span style="color: #dd0000;">"/" </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">nam</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;">"Time: " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">this</span><span style="color: #007700;">.</span><span style="color: #0000bb;">gio </span><span style="color: #007700;">+ </span><span style="color: #dd0000;">": " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">this</span><span style="color: #007700;">.</span><span style="color: #0000bb;">phut </span><span style="color: #007700;">+ </span><span style="color: #dd0000;">": " </span><span style="color: #007700;">+ </span><span style="color: #0000bb;">this</span><span style="color: #007700;">.</span><span style="color: #0000bb;">giay</span><span style="color: #007700;">);<br />        }<br />    }<br />}<br /><br />public class </span><span style="color: #0000bb;">JavaAndroidVn </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;">ThoiGian tg </span><span style="color: #007700;">= new </span><span style="color: #0000bb;">ThoiGian</span><span style="color: #007700;">();<br />        </span><span style="color: #0000bb;">ThoiGian</span><span style="color: #007700;">.</span><span style="color: #0000bb;">Time time </span><span style="color: #007700;">= </span><span style="color: #0000bb;">tg</span><span style="color: #007700;">.new </span><span style="color: #0000bb;">Time</span><span style="color: #007700;">();<br />        </span><span style="color: #0000bb;">tg</span><span style="color: #007700;">.</span><span style="color: #0000bb;">ngay </span><span style="color: #007700;">= </span><span style="color: #0000bb;">20</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">tg</span><span style="color: #007700;">.</span><span style="color: #0000bb;">thang </span><span style="color: #007700;">= </span><span style="color: #0000bb;">7</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">tg</span><span style="color: #007700;">.</span><span style="color: #0000bb;">nam </span><span style="color: #007700;">= </span><span style="color: #0000bb;">1996</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">time</span><span style="color: #007700;">.</span><span style="color: #0000bb;">gio </span><span style="color: #007700;">= </span><span style="color: #0000bb;">20</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">time</span><span style="color: #007700;">.</span><span style="color: #0000bb;">phut </span><span style="color: #007700;">= </span><span style="color: #0000bb;">22</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">time</span><span style="color: #007700;">.</span><span style="color: #0000bb;">giay </span><span style="color: #007700;">= </span><span style="color: #0000bb;">01</span><span style="color: #007700;">;<br />        </span><span style="color: #0000bb;">time</span><span style="color: #007700;">.</span><span style="color: #0000bb;">showTime</span><span style="color: #007700;">();<br /><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;"><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" /> <span style="font-size: 15px;"><span style="color: #141414;">Làm lại thành thạo các ví dụ trên!</span></span></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;" /><b style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;">Đọc thêm:</b><span style="background-color: white; color: #141414; font-family: Roboto, arial, sans-serif; font-size: 15px; line-height: 21px;"> </span><a class="internalLink" href="http://android.vn/threads/cac-lop-con-lop-long-nhau-trong-lap-trinh-java.23905/" 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;">Các lớp con (lớp lồng nhau) trong lập trình Java</a>

Bài 20: Inner class trong Java

1, Khái niệm: Một class nằm trong class khác được gọi là  inner class . Inner class có thể coi như một thuộc tính của class. Nghĩa là bạn kh...

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