文章目錄

• Java 回調 (Callback) 接口學習使用
• • 1.什么是回調(Callback)？
  • 2.Java代碼示例
  • 2.直接調用
  • 3.接口調用
  • 4.Lambda表達式

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Java 回調 (Callback) 接口學習使用

1.什么是回調(Callback)？

回調函數，簡稱回調，是指通過函數參數傳遞到其他代碼的某一塊可執行代碼的引用，這一設計允許了底層代碼調用在高層定義的子程序。

簡單來說：A調用了B的b()方法,那b方法如果包含對A中實現的邏輯的調用，這個過程就被稱作回調。

2.Java代碼示例

package callback;public class MQ {class Producer{public void send(String msg, MsgStateCallback msgStateCallback) {System.out.println("send msg :" + msg);int ACK = 1;if (ACK == 0){msgStateCallback.succ();}else {msgStateCallback.fail();}}}interface MsgStateCallback{void succ();void fail();}public static void main(String[] args) {MQ mq = new MQ();Producer producer = mq.new Producer();String msg = "my msg";producer.send(msg, new MsgStateCallback() {@Overridepublic void succ() {System.out.println("消息發送成功");}@Overridepublic void fail() {System.out.println("消息發送失敗");}});} }

2.直接調用

將參數改成Callback示例

package callback;public class DirectCallback {class Request{public void send(InvokeCallback.CallBack callBack) throws Exception {// 模擬等待響應Thread.sleep(3000);System.out.println("[Request]:收到響應");callBack.processResponse();}}public static void main(String[] args) throws InterruptedException {DirectCallback directCallback = new DirectCallback();final Request request = directCallback.new Request();System.out.println("發送請求");new Thread(new Runnable() {@Overridepublic void run() {try {request.send(new InvokeCallback.CallBack());} catch (Exception e) {e.printStackTrace();}}}).start();System.out.println("請求已經發送");Thread.sleep(10 * 1000);}}

3.接口調用

Callback作為接口傳入參數

Java代碼示例中就是接口調用方式！！！

package callback;import java.lang.reflect.Method;public class InterfaceCallback {class Request{public void send(ResponseCallback responseCallback) throws Exception {Thread.sleep(3000);responseCallback.processResponse();}}interface ResponseCallback{void processResponse();}public static void main(String[] args) throws InterruptedException {InterfaceCallback interfaceCallback = new InterfaceCallback();final Request request = interfaceCallback.new Request();System.out.println("發送請求");new Thread(new Runnable() {@Overridepublic void run() {try {request.send(new ResponseCallback() {@Overridepublic void processResponse() {System.out.println("收到響應");}});} catch (Exception e) {e.printStackTrace();}}}).start();System.out.println("請求已發送");Thread.sleep(10000);}}

4.Lambda表達式

package callback;import java.lang.reflect.Method;public class LambdaCallback {class Request{public void send(ResponseCallback responseCallback) throws Exception {Thread.sleep(3000);responseCallback.processResponse();}}interface ResponseCallback{void processResponse();}public static void main(String[] args) throws Exception {LambdaCallback lambdaCallback = new LambdaCallback();Request request = lambdaCallback.new Request();System.out.println("發送請求");new Thread(() -> {try {request.send(() -> System.out.println("處理響應"));} catch (Exception e) {e.printStackTrace();}} ).start();System.out.println("請求已發送");}}

參考博客：

https://juejin.im/post/6844904066129084429

http://gaocegege.com/Blog/java/java-callback

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