GUC-9 ReadWriteLock : 讀寫鎖

 

import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/*
 * 1. ReadWriteLock : 讀寫鎖
 * 
 * 寫寫/讀寫 須要「互斥」
 * 讀讀 不須要互斥
 * 
 */
public class TestReadWriteLock {

    public static void main(String[] args) {
        ReadWriteLockDemo rw = new ReadWriteLockDemo();
        
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                rw.set((int)(Math.random() * 101));
            }
        }, "Write:").start();
        
        
        for (int i = 0; i < 100; i++) {
            new Thread(new Runnable() {
                
                @Override
                public void run() {
                    rw.get();
                }
            }).start();
        }
    }
    
}

class ReadWriteLockDemo{
    
    private int number = 0;
    
    private ReadWriteLock lock = new ReentrantReadWriteLock();
    
    //讀
    public void get(){
        lock.readLock().lock(); //上鎖
        
        try{
            System.out.println(Thread.currentThread().getName() + " : " + number);
        }finally{
            lock.readLock().unlock(); //釋放鎖
        }
    }
    
    //寫
    public void set(int number){
        lock.writeLock().lock();
        
        try{
            System.out.println(Thread.currentThread().getName());
            this.number = number;
        }finally{
            lock.writeLock().unlock();
        }
    }
}