Java中线程中断的几种方法小结
作者:爪哇码农
使用线程的stop()来中断线程
这种方式是直接调用线程的stop()方法,可以直接让线程终止运行,是一种很暴力的方式。
public static void test02(){ Thread thread1 = new Thread(()->{ System.out.println("thread1启动了"); while (true){ System.out.println("thread1循环中..."); } }); thread1.start(); try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("准备关闭thread1线程"); thread1.stop(); System.out.println("主线程停止"); }
运行结果如下
使用线程的interrupt()来中断线程
public static void testInterrupt(){ Thread thread1 = new Thread(() -> { while (true){ boolean interrupted = Thread.currentThread().isInterrupted(); if(interrupted){ System.out.println("thread1线程被中断"); break; } System.out.println("thread1循环中..."); } }); thread1.start(); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } thread1.interrupt(); }
运行结果如下
interrupt相比于stop中断线程的方式更加温柔,当主线程调用thread1线程的interrupt方法其实本质就是将thread1线程的中断标志设置为true,仅此而已。被设置中断标志的线程还是可以继续运行的,不受影响,也就是如果thread不主动结束线程该线程是不会停止的。
代码演示如下
public static void testInterrupt2(){ Thread thread1 = new Thread(() -> { while (true){ boolean interrupted = Thread.currentThread().isInterrupted(); System.out.println("当前中断标志位状态为:"+interrupted); System.out.println("thread1循环中..."); } }); thread1.start(); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } thread1.interrupt(); }
运行结果如下
当调用了thread1.interrupt();之后thread1还会一直无限执行下去。
如果thread1线程处于被阻塞状态(例如处于sleep,wait,join等状态),在别的线程调用thread1的interrupt方法,那么线程的中断状态会被清除,并抛出InterruptedException异常
代码如下
public static void testInterrupt3(){ Thread thread1 = new Thread(() -> { System.out.println("thread1线程启动了。。。"); try { Thread.sleep(10000); } catch (InterruptedException e) { e.printStackTrace(); } }); thread1.start(); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } thread1.interrupt(); }
运行结果如下
1.线程启动是,默认中断标志位为false
2.如果main线程调用了thread1的interrupt()方法,中断标志位就变成了true
3.正常情况,中断标志位为true,如果thread1判断中断标志位为true就中断执行,则thread1停止,如果thread1线程自己不终止运行则不会停止。
4.异常情况,如果thread1线程正处于阻塞状态(例如处于sleep,wait,join等状态),将会把中断状态清除,并且将抛出InterruptedException异常,此时中断标志位还是false,thread1线程还会继续执行。
测试异常情况,并且循环不停止的情况,代码如下
public static void testInterrupt4(){ Thread thread1 = new Thread(() -> { System.out.println("thread1线程启动了。。。"); try { Thread.sleep(5000); } catch (Exception e) { e.printStackTrace(); } while (true){ boolean interrupted = Thread.currentThread().isInterrupted(); if(interrupted){ System.out.println("thread1程序终止"); break; } } }); thread1.start(); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } thread1.interrupt(); }
程序并没有停止
5.解决异常情况的方法,就是在catch块中,需要再次将中断标志位设置为true,2次调用才能使中断标志位改为true
public static void testInterrupt5(){ Thread thread1 = new Thread(() -> { System.out.println("thread1线程启动了。。。"); try { Thread.sleep(5000); } catch (Exception e) { // 抛出异常过后在此调用interrupt方法 Thread.currentThread().interrupt(); e.printStackTrace(); } while (true){ boolean interrupted = Thread.currentThread().isInterrupted(); if(interrupted){ System.out.println("thread1程序终止"); break; } } }); thread1.start(); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } thread1.interrupt(); }
关于Thread.interrupted()方法
判断线程是否被中断并清除当前中断状态
这个方法做了两件事情
1.返回当前线程的中断状态
2.将当前线程的中断状态清零并重新设置为false,清除线程的中断状态
public static void testInterrupt6(){ System.out.println(Thread.currentThread().getName() + "\t" + Thread.interrupted()); System.out.println(Thread.currentThread().getName() + "\t" + Thread.interrupted()); System.out.println("1111111111111111"); // 中断标志位设置为true Thread.currentThread().interrupt(); System.out.println("2222222222222222"); System.out.println(Thread.currentThread().getName() + "\t" + Thread.interrupted()); System.out.println(Thread.currentThread().getName() + "\t" + Thread.interrupted()); }
关于isInterrupted()方法
该方法只会返回当前线程的中断标志位的状态;不会清除当前线程的中断标志位的状态
public static void testInterrupt7(){ System.out.println(Thread.currentThread().getName() + "\t" + Thread.currentThread().isInterrupted()); System.out.println(Thread.currentThread().getName() + "\t" + Thread.currentThread().isInterrupted()); System.out.println("1111111111111111"); // 中断标志位设置为true Thread.currentThread().interrupt(); System.out.println("2222222222222222"); System.out.println(Thread.currentThread().getName() + "\t" + Thread.currentThread().isInterrupted()); System.out.println(Thread.currentThread().getName() + "\t" + Thread.currentThread().isInterrupted()); }
关于Thread的静态方法interrupted和Thread实例方法isInterrupted底层源码
1.interrupted
public static boolean interrupted() { return currentThread().isInterrupted(true); }
2.isInterrupted
public boolean isInterrupted() { return isInterrupted(false); }
本质上都是调用了实例的isInterrupted方法,只是传入的参数有所不同,当传入true时,会情空当前线程的中断标志,重置为false,方传入false时,不会清空。
private native boolean isInterrupted(boolean ClearInterrupted);
该方法是被native修饰的方法
总结
- public void interrupt() 其中interrupt()是一个实例方法
它通知目标线程中断,也仅仅是设置目标线程的中断标志位为true. - public boolean isInterrupted() 其中isInterrupted()方法也是一个实例方法
它判断当前线程是否被中断(通过检查中断标志位)并获得中断标志 - public static boolean interrupted() . 该方法是Thread类的静态方法
返回当前线程的中断状态真实值后会将当前线程的中断状态设置为false,此方法调用之后会清除当前线程的中断标志位的状态。
通过共享变量来控制
1.使用volatile 关键字来实现线程中断
static volatile boolean run = true; public static void main(String[] args) { new Thread(()->{ while (run){ System.out.println("线程1执行中..."); } }).start(); try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } run = false; System.out.println("主线程结束"); }
2.使用同步代码块synchronized来实现线程中断
static boolean run = true; static Object object = new Object(); public static void main(String[] args) { new Thread(()->{ while (run){ System.out.println("线程1执行中..."); synchronized (object){ } } }).start(); try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } run = false; System.out.println("主线程结束"); }
3.使用AtomicBoolean 来实现线程中断
public static void main(String[] args) { AtomicBoolean run = new AtomicBoolean(true); new Thread(()->{ while (run.get()){ System.out.println("线程1执行中..."); } }).start(); try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } run.set(false); System.out.println("主线程结束"); }
其运行结果如下
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