Java线程间通信-等待唤醒机制

落日映苍穹つ 2022-06-17 14:11 239阅读 0赞

线程之间的关系是平等的，彼此之间并不存在任何依赖，它们各自竞争CPU资源，互不相让，并且还无条件地阻止其他线程对共享资源的异步访问。然而，也有很多现实问题要求不仅要同步的访问同一共享资源，而且线程间还彼此牵制，通过相互通信来向前推进。

下面程序将通过等待唤醒机制实现线程间通信。

package com.javase.thread;
    
    public class InputOutputDemo {
    	
    	static boolean lockFlag = false;
    	public static void main(String[] args) {
    		Resource r = new Resource();
    		new Thread(new Input(r)).start();
    		new Thread(new Output(r)).start();
    		
    	}
    }
    
    class Resource{
    	private String name;
    	private String sex;
    	public String getName() {
    		return name;
    	}
    	public String getSex() {
    		return sex;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public void setSex(String sex) {
    		this.sex = sex;
    	}
    	
    }
    
    class Input implements Runnable{
    	private Resource r ;
    	boolean flag = false;
    	public Input(Resource r){
    		this.r=r;
    	}
    	public void run(){
    		while(true){
    			synchronized(r){
    				if(InputOutputDemo.lockFlag){
    					try {
    						r.wait();
    					} catch (InterruptedException e) {
    						e.printStackTrace();
    					}
    				}
    				if(flag){
    					r.setName("alex");
    					r.setSex("male");
    					flag=false;
    				}else{
    					r.setName("dd");
    					r.setSex("female");
    					flag=true;
    				}
    				InputOutputDemo.lockFlag=true;
    				r.notify();
    			}
    			
    		}
    	}
    }
    
    class Output implements Runnable{
    	private Resource r;
    	public Output(Resource r){
    		this.r=r;
    	}
    	public void run(){
    		while(true){
    			synchronized(r){
    				if(!InputOutputDemo.lockFlag){
    					try {
    						r.wait();
    					} catch (InterruptedException e) {
    						e.printStackTrace();
    					}
    				}
    				System.out.println("name:"+r.getName()+"   sex:"+r.getSex());
    				InputOutputDemo.lockFlag=false;
    				r.notify();
    			}
    			
    		}
    	}
    }

运行结果：

name:dd sex:female  
name:alex sex:male  
name:dd sex:female  
name:alex sex:male  
name:dd sex:female  
name:alex sex:male  
name:dd sex:female

......

以下代码也可获得相同的运行结果：

package com.javase.thread;
    
    public class InputOutputDemo {
    	
    	static boolean lockFlag = false;
    	public static void main(String[] args) {
    		Resource r = new Resource();
    		new Thread(new Input(r)).start();
    		new Thread(new Output(r)).start();
    		
    	}
    }
    
    class Resource{
    	private String name;
    	private String sex;
    	boolean flag = false;
    	public synchronized void set(String name , String sex){
    		if(flag){
    			try {
    				this.wait();
    			} catch (InterruptedException e) {
    				e.printStackTrace();
    			}
    		}
    		this.name=name;
    		this.sex=sex;
    		flag=true;
    		this.notify();
    	}
    	public synchronized void print(){
    		if(!flag){
    			try {
    				this.wait();
    			} catch (InterruptedException e) {
    				e.printStackTrace();
    			}
    		}
    		System.out.println("name:"+name+"   sex:"+sex);
    		flag=false;
    		this.notify();
    	}
    	
    }
    
    class Input implements Runnable{
    	private Resource r ;
    	boolean flag = false;
    	public Input(Resource r){
    		this.r=r;
    	}
    	public void run(){
    		while(true){
    			if(flag){
    				r.set("alex", "male");
    				flag=false;
    			}else{
    				r.set("dd", "female");
    				flag=true;
    			}
    			
    		}
    	}
    }
    
    class Output implements Runnable{
    	private Resource r;
    	public Output(Resource r){
    		this.r=r;
    	}
    	public void run(){
    		while(true){
    			r.print();
    		}
    	}
    }