java：lock中使用多个condition实现通知特定线程

相对于synchronized块中使用notify或者notifyall，通知的线程都是不确定的，当发一个通知，并不知道

下一个竞争到所得会是哪个线程。

而lock更加细腻，通过多个condition，则可以实现通知部分线程的功能。

service类：

package service; import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; public class MyService { private Lock lock = new ReentrantLock(); public Condition conditionA = lock.newCondition(); //两个condition public Condition conditionB = lock.newCondition(); public void awaitA() { try { lock.lock(); System.out.println("begin awaitA时间为" + System.currentTimeMillis() + " ThreadName=" + Thread.currentThread().getName()); conditionA.await(); //用conditiona等待。 System.out.println(" end awaitA时间为" + System.currentTimeMillis() + " ThreadName=" + Thread.currentThread().getName()); } catch (InterruptedException e) { e.printStackTrace(); } finally { lock.unlock(); } } public void awaitB() { try { lock.lock(); System.out.println("begin awaitB时间为" + System.currentTimeMillis() + " ThreadName=" + Thread.currentThread().getName()); conditionB.await(); System.out.println(" end awaitB时间为" + System.currentTimeMillis() + " ThreadName=" + Thread.currentThread().getName()); } catch (InterruptedException e) { e.printStackTrace(); } finally { lock.unlock(); } } public void signalAll_A() { try { lock.lock(); System.out.println(" signalAll_A时间为" + System.currentTimeMillis() + " ThreadName=" + Thread.currentThread().getName()); conditionA.signalAll(); //用a来打开。 } finally { lock.unlock(); } } public void signalAll_B() { try { lock.lock(); System.out.println(" signalAll_B时间为" + System.currentTimeMillis() + " ThreadName=" + Thread.currentThread().getName()); conditionB.signalAll(); } finally { lock.unlock(); } } }

两个线程包装类：

package extthread; import service.MyService; public class ThreadA extends Thread { private MyService service; public ThreadA(MyService service) { super(); this.service = service; } @Override public void run() { service.awaitA(); } }

package extthread; import service.MyService; public class ThreadB extends Thread { private MyService service; public ThreadB(MyService service) { super(); this.service = service; } @Override public void run() { service.awaitB(); } } 运行类：

package test; import service.MyService; import extthread.ThreadA; import extthread.ThreadB; public class Run { public static void main(String[] args) throws InterruptedException { MyService service = new MyService(); ThreadA a = new ThreadA(service); a.setName("A"); a.start(); ThreadB b = new ThreadB(service); b.setName("B"); b.start(); Thread.sleep(3000); service.signalAll_A(); } }

当是conditionA等待时，conditionB的signal方法时无法唤醒的。