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使用Condition实现多路等待通知

程序员文章站 2024-01-07 23:12:52
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一个锁内部可以有多个Condition,即有多路等待和通知,可参考JDK1.5的Lock和Condition实现的可阻塞队列的应用案例,在传统的线程机制中一个监视器对象上只能有一路等待和通知,要想实现多路等待和通知,必须嵌套使用多个同步监视器对象.

使用Condition可简单实现多路等待通知

public class TwoConditionCommunication {
	
	public static void main(String[] args) {

		final Business business = new Business();
		new Thread(new Runnable() {

			@Override
			public void run() {

				for (int i = 1; i <= 50; i++) {
					business.sub(i);
				}

			}
		}).start();

		for (int i = 1; i <= 50; i++) {
			business.main(i);
		}

	}

	static class Business {
		Lock lock = new ReentrantLock();
		Condition condition_sub = lock.newCondition();
		Condition condition_main = lock.newCondition();
		private boolean shouldSub = true;

		public void sub(int i) {
			lock.lock();
			try {
				while (!shouldSub) {
					try {
						condition_sub.await();
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
				for (int j = 1; j <= 10; j++) {
					System.out.println("sub2 thread sequence of " + j
							+ ",loop of " + i);
				}
				shouldSub = false;
				condition_main.signal();
			} finally {
				lock.unlock();
			}
		}

		public void main(int i) {
			lock.lock();
			try {
				while (shouldSub) {
					try {
						condition_main.await();
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
				for (int j = 1; j <= 20; j++) {
					System.out.println("main thread sequence of " + j
							+ ",loop of " + i);
				}
				shouldSub = true;
				condition_sub.signal();
			} finally {
				lock.unlock();
			}
		}

	}
}

 附JDK1.5中Demo

class BoundedBuffer {
   final Lock lock = new ReentrantLock();
   final Condition notFull  = lock.newCondition(); 
   final Condition notEmpty = lock.newCondition(); 

   final Object[] items = new Object[100];
   int putptr, takeptr, count;

   public void put(Object x) throws InterruptedException {
     lock.lock();
     try {
       while (count == items.length) 
         notFull.await();
       items[putptr] = x; 
       if (++putptr == items.length) putptr = 0;
       ++count;
       notEmpty.signal();
     } finally {
       lock.unlock();
     }
   }

   public Object take() throws InterruptedException {
     lock.lock();
     try {
       while (count == 0) 
         notEmpty.await();
       Object x = items[takeptr]; 
       if (++takeptr == items.length) takeptr = 0;
       --count;
       notFull.signal();
       return x;
     } finally {
       lock.unlock();
     }
   } 
 }
相关标签: j2se concurrent

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