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用interrupt()中断Java线程

發布時間：2024/4/17 java 50 豆豆

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http://hapinwater.iteye.com/blog/310558

最近在學習Java線程相關的東西，和大家分享一下，有錯誤之處歡迎大家指正．

假如我們有一個任務如下，交給一個Java線程來執行，如何才能保證調用interrupt()來中斷它呢？

Java代碼

class ATask implements Runnable{?

??? private double d = 0.0;?

?????

??? public void run() {?

??????? //死循環執行打印"I am running!" 和做消耗時間的浮點計算?

??????? while (true) {?

??????????? System.out.println("I am running!");?

?????????????

??????????? for (int i = 0; i < 900000; i++) {?

??????????????? d =? d + (Math.PI + Math.E) / d;?

??????????? }?

??????????? //給線程調度器可以切換到其它進程的信號?

??????????? Thread.yield();?

??????? }?

??? }?

public class InterruptTaskTest {?

?????

??? public static void main(String[] args) throws Exception{?

??????? //將任務交給一個線程執行?

??????? Thread t = new Thread(new ATask());?

??????? t.start();?

?????????

??????? //運行一斷時間中斷線程?

??????? Thread.sleep(100);?

??????? System.out.println("****************************");?

??????? System.out.println("Interrupted Thread!");?

??????? System.out.println("****************************");?

??????? t.interrupt();?

??? }?

}??

class ATask implements Runnable{private double d = 0.0;public void run() {//死循環執行打印"I am running!" 和做消耗時間的浮點計算while (true) {System.out.println("I am running!");for (int i = 0; i < 900000; i++) {d = d + (Math.PI + Math.E) / d;}//給線程調度器可以切換到其它進程的信號Thread.yield();}} }public class InterruptTaskTest {public static void main(String[] args) throws Exception{//將任務交給一個線程執行Thread t = new Thread(new ATask());t.start();//運行一斷時間中斷線程Thread.sleep(100);System.out.println("****************************");System.out.println("Interrupted Thread!");System.out.println("****************************");t.interrupt();} }

運行這個程序，我們發現調用interrupt()后，程序仍在運行，如果不強制結束，程序將一直運行下去，如下所示:

Java代碼

......?

I am running!?

****************************?

Interrupted Thread!?

****************************?

I am running!?

....?

...... I am running! I am running! I am running! I am running! **************************** Interrupted Thread! **************************** I am running! I am running! I am running! I am running! I am running! ....

雖然中斷發生了，但線程仍然在進行，離開線程有兩種常用的方法：
拋出InterruptedException和用Thread.interrupted()檢查是否發生中斷,下面分別看一下這兩種方法：
1.在阻塞操作時如Thread.sleep()時被中斷會拋出InterruptedException(注意，進行不能中斷的IO操作而阻塞和要獲得對象的鎖調用對象的synchronized方法而阻塞時不會拋出InterruptedException)

Java代碼

class ATask implements Runnable{?

??? private double d = 0.0;?

?????

??? public void run() {?

??????? //死循環執行打印"I am running!" 和做消耗時間的浮點計算?

??????? try {?

??????????? while (true) {?

??????????????? System.out.println("I am running!");?

?????????????????

??????????????? for (int i = 0; i < 900000; i++) {?

??????????????????? d =? d + (Math.PI + Math.E) / d;?

??????????????? }?

??????????????? //休眠一斷時間,中斷時會拋出InterruptedException?

??????????????? Thread.sleep(50);?

??????????? }?

??????? } catch (InterruptedException e) {?

??????????? System.out.println("ATask.run() interrupted!");?

??????? }?

??? }?

class ATask implements Runnable{private double d = 0.0;public void run() {//死循環執行打印"I am running!" 和做消耗時間的浮點計算try {while (true) {System.out.println("I am running!");for (int i = 0; i < 900000; i++) {d = d + (Math.PI + Math.E) / d;}//休眠一斷時間,中斷時會拋出InterruptedExceptionThread.sleep(50);}} catch (InterruptedException e) {System.out.println("ATask.run() interrupted!");}} }

程序運行結果如下:

Java代碼

I am running!?

****************************?

Interrupted Thread!?

****************************?

ATask.run() interrupted!?

I am running! I am running! **************************** Interrupted Thread! **************************** ATask.run() interrupted!

可以看到中斷任務時讓任務拋出InterruptedException來離開任務．

2.Thread.interrupted()檢查是否發生中斷.Thread.interrupted()能告訴你線程是否發生中斷,并將清除中斷狀態標記，所以程序不會兩次通知你線程發生了中斷．

Java代碼

class ATask implements Runnable{?

??? private double d = 0.0;?

?????

??? public void run() {?

?????????

??????? //檢查程序是否發生中斷?

??????? while (!Thread.interrupted()) {?

??????????? System.out.println("I am running!");?

??????????? for (int i = 0; i < 900000; i++) {?

??????????????? d = d + (Math.PI + Math.E) / d;?

??????????? }?

??????? }?

??????? System.out.println("ATask.run() interrupted!");?

??? }?

class ATask implements Runnable{private double d = 0.0;public void run() {//檢查程序是否發生中斷while (!Thread.interrupted()) {System.out.println("I am running!");for (int i = 0; i < 900000; i++) {d = d + (Math.PI + Math.E) / d;}}System.out.println("ATask.run() interrupted!");} }

程序運行結果如下：

Java代碼

I am running!?

****************************?

Interrupted Thread!?

****************************?

ATask.run() interrupted!?

I am running! I am running! I am running! I am running! I am running! I am running! I am running! **************************** Interrupted Thread! **************************** ATask.run() interrupted!

我們可結合使用兩種方法來達到可以通過interrupt()中斷線程.請看下面例子:

Java代碼

class ATask implements Runnable{?

??? private double d = 0.0;?

?????

??? public void run() {?

?????????

??????? try {?

??????? //檢查程序是否發生中斷?

??????? while (!Thread.interrupted()) {?

??????????? System.out.println("I am running!");?

??????????? //point1 before sleep?

??????????? Thread.sleep(20);?

??????????? //point2 after sleep?

??????????? System.out.println("Calculating");?

??????????? for (int i = 0; i < 900000; i++) {?

??????????????? d = d + (Math.PI + Math.E) / d;?

??????????? }?

??????? }?

?????????

??????? } catch (InterruptedException e) {?

??????????? System.out.println("Exiting by Exception");?

??????? }?

?????????

??????? System.out.println("ATask.run() interrupted!");?

??? }?

class ATask implements Runnable{private double d = 0.0;public void run() {try {//檢查程序是否發生中斷while (!Thread.interrupted()) {System.out.println("I am running!");//point1 before sleepThread.sleep(20);//point2 after sleepSystem.out.println("Calculating");for (int i = 0; i < 900000; i++) {d = d + (Math.PI + Math.E) / d;}}} catch (InterruptedException e) {System.out.println("Exiting by Exception");}System.out.println("ATask.run() interrupted!");} }

在point1之前處point2之后發生中斷會產生兩種不同的結果，可以通過修改InterruptTaskTest main()里的Thread.sleep()的時間來達到在point1之前產生中斷或在point2之后產生中斷.
如果在point1之前發生中斷，程序會在調用Thread.sleep()時拋出InterruptedException從而結束線程．這和在Thread.sleep()時被中斷是一樣的效果.程序運行結果可能如下：

Java代碼

I am running!?

Calculating?

I am running!?

Calculating?

I am running!?

Calculating?

I am running!?

****************************?

Interrupted Thread!?

****************************?

Exiting by Exception?

ATask.run() interrupted!?

I am running! Calculating I am running! Calculating I am running! Calculating I am running! **************************** Interrupted Thread! **************************** Exiting by Exception ATask.run() interrupted!

如果在point2之后發生中斷，線程會繼續執行到下一次while判斷中斷狀態時．程序運行結果可能如下：

Java代碼

I am running!?

Calculating?

I am running!?

Calculating?

I am running!?

Calculating?

****************************?

Interrupted Thread!?

****************************?

ATask.run() interrupted!?

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