JAVA多线程--信号量(Semaphore)

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

public class SemaPhore {
public static void main(String[] args) {
// 线程池
ExecutorService exec = Executors.newCachedThreadPool();
// 只能5个线程同时访问
final Semaphore semp = new Semaphore(5);
// 模拟15个客户端访问
for (int index = 0; index < 15; index++) {
final int NO = index;
Runnable run = new Runnable() {
public void run() {
try {
// 获取许可
semp.acquire();
System.out.println("Accessing: " + NO);
Thread.sleep((long) (Math.random() * 6000));
// 访问完后，释放
semp.release();
//availablePermits()指的是当前信号灯库中有多少个可以被使用
System.out.println("-----------------" + semp.availablePermits());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
exec.execute(run);
}
// 退出线程池
exec.shutdown();
}
}

C:\Users\QingrouShui\Desktop>java SemaPhore
Accessing: 0
Accessing: 2
Accessing: 1
Accessing: 4
Accessing: 3
Accessing: 6
-----------------0
-----------------1
Accessing: 5
-----------------1
Accessing: 7
-----------------1
Accessing: 8
-----------------1
Accessing: 9
-----------------1
Accessing: 10
-----------------1
Accessing: 11
-----------------1
Accessing: 12
Accessing: 13
-----------------0
-----------------1
Accessing: 14
-----------------1
-----------------2
-----------------3
-----------------4
-----------------5