Java并发编程实践:利用信号量实现阻塞集合demo

package com.rx.wwx;

import java.util.HashSet;
import java.util.Random;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

public class BlockingSet {

    private final Set set;
    private final Semaphore semaphore;
    private int capacity;

    public BlockingSet(Set set, int capacity) {
        this.set = set;
        semaphore = new Semaphore(capacity);
        this.capacity = capacity;
    }

    public boolean add(T t) throws InterruptedException {
        semaphore.acquire();
        boolean add = set.add(t);
        if (!add) {
            semaphore.release();
        }
        return add;
    }

    public boolean remove(T t) {
        boolean remove = set.remove(t);
        if (remove) {
            semaphore.release();
        }
        return remove;
    }

    public void removeAll() {
        set.clear();
        semaphore.release(capacity);
    }

    public static void main(String[] args) {
        ExecutorService executorService =
                Executors.newFixedThreadPool(10);

        final BlockingSet blockingSet = new BlockingSet<>(new HashSet(), 5);

        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                try {
                    System.out.println(Thread.currentThread().getId() + ":尝试往集合添加元素");
                    blockingSet.add(new Random().nextInt(100));
                    System.out.println(Thread.currentThread().getId() + ":添加成功");
                } catch (Throwable throwable) {
                    throwable.printStackTrace();
                }
            }
        };

        for (int i = 0; i < 10; i++) {
            executorService.execute(runnable);
        }

        new Thread(new Runnable() {
            @Override
            public void run() {
                try{
                    System.out.println("先暂停3秒，注意观察他们是否在阻塞后又继续添加");
                    Thread.sleep(3000);
                    blockingSet.removeAll();
                }catch (Throwable throwable){
                    throwable.printStackTrace();
                }
            }
        }).start();

    }

}

运行结果：