Semaphore：Semaphores are often used to restrict the number of threads than can access some (physical or logical) resource.

import java.util.LinkedList;import java.util.List;import java.util.Random;import java.util.concurrent.Semaphore;class Buffer {    List
     
       buffer = new LinkedList
      
       ();    // 互斥量，控制buffer的互斥访问    private Semaphore mutex = new Semaphore(1);    // canProduceCount可以生产的数量（表示缓冲区可用的数量）。 通过生产者调用acquire，减少permit数目    private Semaphore canProduceCount = new Semaphore(10);    // canConsumerCount可以消费的数量。通过生产者调用release，增加permit数目    private Semaphore canConsumerCount = new Semaphore(0);    Random rn = new Random(10);    public void get() throws InterruptedException {        canConsumerCount.acquire();        try {            mutex.acquire();            int val = buffer.remove(0);            System.out                    .println(Thread.currentThread().getName() + " 正在消费数据为：" + val + "    buffer目前大小为：" + buffer.size());        } finally {            mutex.release();            canProduceCount.release();        }    }    public void put() throws InterruptedException {        canProduceCount.acquire();        try {            mutex.acquire();            int val = rn.nextInt(10);            buffer.add(val);            System.out                    .println(Thread.currentThread().getName() + " 正在生产数据为：" + val + "    buffer目前大小为：" + buffer.size());        } finally {            mutex.release();            // 生产者调用release，增加可以消费的数量            canConsumerCount.release();        }    }}public class SemaphoreProducerComsumer1 {    public static void main(String[] args) {        final Buffer buffer = new Buffer();        startProducer(buffer);        startProducer(buffer);        startConsumer(buffer);        startConsumer(buffer);    }    public static void startProducer(final Buffer buffer) {        new Thread(new Runnable() {            @Override            public void run() {                try {                    while (true) {                        buffer.put();                    }                } catch (Exception e) {                    e.printStackTrace();                }            }        }).start();    }    public static void startConsumer(final Buffer buffer) {        new Thread(new Runnable() {            @Override            public void run() {                try {                    while (true) {                        buffer.get();                    }                } catch (Exception e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }            }        }).start();    }}