控制并发线程数的Semaphore

Semaphore(信号量)使用来控制同时访问特定资源的线程数量.它通过协调各个线程,以保证合理的使用公共资源.
可以把它比作是控制流量的红绿灯.

public class SemaphoreTest {

private static final int THREAD_COUNT = 30;
private static ExecutorService threadPool = Executors.newFixedThreadPool(THREAD_COUNT);

private Semaphore s = new Semaphore(10);

public static void main(String [] args) {
    for(int i = 0; i< THREAD_COUNT; i++) {
        threadPool.execute(
            new Runnable() {
                public void run() {
                    try {
                        s.acquire();
                        System.out.println("save data");
                        s.release();
                    }
                }
            }
        );
    }
    threadPool.shutDown();
}

}