java实现PV操作

package com.jayfulmath.designpattern.command;

import java.util.concurrent.Semaphore;

/*
    P(S):
    
    ①将信号量S的值减1,即S=S-1;
    
    ②如果S>=0,则该进程继续执行;否则该进程置为等待状态。
    
    V(S):
    
    ①将信号量S的值加1,即S=S+1;
    
    ②该进程继续执行;如果该信号的等待队列中有等待进程就唤醒一等待进程。
 * 
 * */
public class PVObject {
    
    private Semaphore mSemaphore =null;
    private int Max_size = 0xff;
    private String name = null;
    public PVObject(int size,String name)
    {
        if(size>0)
        {
            Max_size = size;
            mSemaphore = new Semaphore(size);
        }
        this.name = name;
    }
    
    public PVObject(String name)
    {
        Max_size = 1;
        mSemaphore = new Semaphore(1);
        this.name = name;
    }
    
    public void Init(int status)
    {
        if(status<0 || status>Max_size)
        {
            System.out.println("[PVObject][Init]"+name+" wrong,status:"+status);
            return;
        }
        
        if(status == Max_size)
        {
            return;
        }
        
        try {
            mSemaphore.release(Max_size);
            mSemaphore.acquire(Max_size-status);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }    
    }
    
    public void P()
    {
        try {
            //
            mSemaphore.acquire();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }        
    }
    
    public void V()
    {
        mSemaphore.release();        
    }
}
Max_size 为允许同时使用信号量的个数,默认情况是1个。

posted on 2014-12-25 14:40  Joyfulmath  阅读(1501)  评论(0编辑  收藏  举报

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