他可以在线程任意位置让线程阻塞,
LockSupport的静态方法park()可以阻塞当前线程,类似的还有parkNanos() ParkUntil()等,他们实现了一个限时等待
public class LockSupportDemo { public static Object u = new Object(); static ChangeObjectThread t1 = new ChangeObjectThread("t1"); static ChangeObjectThread t2 = new ChangeObjectThread("t2"); public static class ChangeObjectThread extends Thread { public ChangeObjectThread(String name) { super.setName(name); } public void run() { synchronized (u) { System.out.println("in" + getName()); LockSupport.park(); } } } public static void main(String[] args) throws InterruptedException { t1.start(); Thread.sleep(100); t2.start(); LockSupport.unpark(t1); LockSupport.unpark(t2); t1.join(); t2.join(); } }
我们可以使用park()和unpark()方法替换掉以往的suspend()和resume()方法.当然我们依然无法保证unpark()方法发生在park(0方法之后,当时执行这段代码,你会发现,它自始至终都可以正常结束,不会因为park()方法二导致线程永久性的挂起,
这是因为LockSupport类使用类似信号量的机制,他为每一个线程准备了一个许可.这个特点使得:即使unpark()操作发生在park()之前,它也可以使下一次的park()操作立即返回.这也就是上述代码可顺利结束的主要原因.
出来有定时阻塞的功能外,还支持中断影响,但是和其他接收中断函数不一样,他不会抛出InterruptedException异常,他只会默默的返回,但是我们可以从Thread.Interrupted()等方法获得中断标记.
public class LockSupportIntDemo { public static Object u = new Object(); static ChangeObjectThread t1 = new ChangeObjectThread("t1"); static ChangeObjectThread t2 = new ChangeObjectThread("t2"); public static class ChangeObjectThread extends Thread { public ChangeObjectThread(String name) { super.setName(name); } public void run() { synchronized (u) { System.out.println("in " + getName()); LockSupport.park(); if (Thread.interrupted()) { System.out.println(getName() + " 被中断了!"); } } System.out.println(getName() + " 执行结束"); } } public static void main(String[] args) throws InterruptedException { t1.start(); Thread.sleep(100); t2.start(); t1.interrupt(); LockSupport.unpark(t2); } }
时间: 2024-10-21 06:30:46