通过一个有趣的例子说明线程的工作机制

秒速五厘米 2022-07-15 16:18 184阅读 0赞

public class ThreadTestDemo {
    	
    	private int threadNum;//当前线程
    	private int num;//输出的数字
    	public ThreadTestDemo(int threadNum, int num) {
    		super();
    		this.threadNum = threadNum;
    		this.num = num;
    	}
    	//内部线程类
    	static class PrintThread extends Thread{
    
    		private int mThreadNum;//线程数
    		private ThreadTestDemo demo;//当前所在的类
    		
    		public PrintThread(int threadNum,ThreadTestDemo demo) {
    			this.mThreadNum = threadNum;
    			this.demo = demo;
    		}
    		
    		@Override
    		public void run() {
    			System.out.println("当前线程是："+ mThreadNum);
    			//为demo上锁，每次只能有一个线程执行，这是关键
    			synchronized (demo) {
    				for(int i = 1;i<= 3;i++){
    					while(true){
    						System.out.println("Thread"+mThreadNum+"*****");
    						//如果当前线程是demo中将要运行的线程，则跳出循环，否则说明其他线程正在运行，资源被占用，demo等待
    						if(mThreadNum == demo.threadNum){
    							System.out.println("Thread "+mThreadNum+" is running");
    							break;
    						}else{
    							try {
    								demo.wait();
    								System.out.println("demo-thread "+demo.threadNum+" is waiting");
    							} catch (InterruptedException e) {
    								e.printStackTrace();
    							}
    						}
    					}
    					//当前线程抢到资源后，执行循环操作
    					for(int j= 1;j<=5;j++){
    						System.out.println("Thread"+mThreadNum+":"+(++demo.num));
    					}
    					//赋予demo即将要执行的thread,并通知demo
    					demo.threadNum = demo.threadNum%3+1;
    					demo.notifyAll();
    				}
    			}
    		}
    		
    	}