线程中断interrupt()、interrupted()和is
interrupt()
thread.interrupt()，该方法用于中断Thread线程，此线程并非当前线程，而是调用interrupt()方法的实例所代表的线程，并不是强制关闭线程，而是将中断标记位设置为true，线程的中断需要在线程内部协作关闭
interrupted()
interrupted()为静态方法，判断当前线程的中断状态，并会将中断标记位设置为false，在第二次调用时中断状态会返回false
isInterrupted()
thread.isInterrupted()，用于判断thread的中断状态，不清除中断状态
public class MyThread extends Thread {
public MyThread(String name) {
super(name);
}
@Override
public void run() {
for (int i = 0; i < 100; ++i) {
System.out.println("i : " + i);
}
}
}
public class InterruptTest {
public static void main(String[] args) {
MyThread myThread = new MyThread("my-thread");
myThread.start();
// 中断myThread线程，myThread线程的中断标记位设置为true
myThread.interrupt();
System.out.println("myThread.isInterrupted() : " + myThread.isInterrupted());
System.out.println("myThread.isInterrupted() : " + myThread.isInterrupted());
System.out.println("myThread.isAlive() : " + myThread.isAlive());
System.out.println("main.isInterrupted() : " + Thread.currentThread().isInterrupted());
}
}
输出结果：
myThread.isInterrupted() : true
myThread.isInterrupted() : true
myThread.isAlive() : true
main.isInterrupted() : false
结论
- myThread.isInterrupted()结果为true，main.isInterrupted()结果为false，则证明myThread.interrupt()方法是对myThread实例所对应线程设进行的中断操作
- myThread.isInterrupted()执行了两次均返回true，则说明isInterrupted()方法仅仅返回myThread线程的中断状态，不清除中断状态
- myThread.isAlive()结果为true，则证明isInterrupted()并不会直接中断线程，而仅仅是将中断标记位设置为true
public class InterruptedTest {
public static void main(String[] args) {
MyThread myThread = new MyThread("my-thread");
myThread.start();
myThread.interrupt();
Thread.currentThread().interrupt();
System.out.println("执行前-myThread.isInterrupted() : " + myThread.isInterrupted());
System.out.println("执行前-myThread.isInterrupted() : " + myThread.isInterrupted());
System.out.println("执行前-main.isInterrupted() : " + Thread.currentThread().isInterrupted());
System.out.println("执行前-main.isInterrupted() : " + Thread.currentThread().isInterrupted());
System.out.println("main interrupted() : " + Thread.interrupted());
System.out.println("main interrupted() : " + Thread.interrupted());
System.out.println("执行后-myThread.isInterrupted() : " + myThread.isInterrupted());
System.out.println("执行后-myThread.isInterrupted() : " + myThread.isInterrupted());
System.out.println("执行后-main.isInterrupted() : " + Thread.currentThread().isInterrupted());
System.out.println("执行后-main.isInterrupted() : " + Thread.currentThread().isInterrupted());
}
}
输出结果：
执行前-myThread.isInterrupted() : true
执行前-myThread.isInterrupted() : true
执行前-main.isInterrupted() : true
执行前-main.isInterrupted() : true
main interrupted() : true
main interrupted() : false
执行后-myThread.isInterrupted() : true
执行后-myThread.isInterrupted() : true
执行后-main.isInterrupted() : false
执行后-main.isInterrupted() : false
结论
- main.isInterrupted()执行前后结果不一致，myThread.isInterrupted()执行前后结果一直，则证明interrupted()方法作用在当前线程
- Thread.interrupted()第一次执行为true，第二次执行为false，则证明该方法会清除中断状态
由于interrupt()方法不是真正的去中断线程，可以在run()方法内判断中断状态，当为true时则去执行停止线程的操作
public class MyThread extends Thread {
public MyThread(String name) {
super(name);
}
@Override
public void run() {
for (int i = 0; i < 100; ++i) {
System.out.println("i : " + i);
boolean interrupted = Thread.currentThread().isInterrupted();
if (interrupted) {
// 判断为中断状态时，执行推出操作
System.out.println("通过this.isInterrupted()检测到中断");
System.out.println("第一个interrupted()"+Thread.interrupted());
System.out.println("第二个interrupted()"+Thread.interrupted());
break;
}
}
}
}
输出结果：
通过this.isInterrupted()检测到中断
第一个interrupted()true
第二个interrupted()false
线程抛出InterruptedException异常时，会重置中断标记位为false，需再次调用interrupt()方法才可推出循环
public class HasInterruptException {
public static void main(String[] args) throws InterruptedException {
MyThread myThread = new MyThread("my-thread");
myThread.start();
Thread.sleep(500);
myThread.interrupt();
}
private static class MyThread extends Thread {
public MyThread(String name) {
super(name);
}
@Override
public void run() {
Thread thread = Thread.currentThread();
while (!thread.isInterrupted()) {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
System.out.println("抛出异常， " + thread.getName() + " interrupt flag is " + thread.isInterrupted());
// 当线程抛出InterruptedException异常时，会重置中断标记位为false，需再次调用interrupt()方法才可推出循环
thread.interrupt();
}
System.out.println(thread.getName() + "运行中...");
}
System.out.println("跳出循环后" + thread.getName() + " interrupt flag is " + thread.isInterrupted());
}
}
}
输出结果
my-thread运行中...
my-thread运行中...
my-thread运行中...
my-thread运行中...
java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)
at com.shawntime.enjoy.concurrency.interrupt.HasInterruptException$MyThread.run(HasInterruptException.java:24)
抛出异常， my-thread interrupt flag is false
my-thread运行中...
跳出循环后my-thread interrupt flag is true
结论
- 当抛出InterruptedException异常时，中断标记位被重置为false
