Java中的信号量

package JavaDay6_02;

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.Semaphore;

/**
 * @author myvina@qq.com
 * @date 18-6-2  上午10:19
 */

public class Demo3<T> {
    private final Set<T> set;
    private final Semaphore sem;

    public Demo3(int bound) {
        this.set = Collections.synchronizedSet(new HashSet<>());
        this.sem = new Semaphore(bound);
    }

    public boolean add(T o) throws InterruptedException {
        sem.acquire();
        boolean wasAdded = false;
        try {
            wasAdded = set.add(o);
            return wasAdded;
        } finally {
            if(!wasAdded) {
                sem.release();;
            }
        }
    }
    
    public boolean remove(Object o) {
        boolean wasRemoved = set.remove(o);
        if(wasRemoved) {
            sem.release();
        }
        return wasRemoved;
    }
}