【1】控制线程执行的顺序

末蓝、 2022-05-14 05:19 147阅读 0赞

> ### **1.join方法** ###

static Thread thread1 =new Thread(new Runnable() {
    		@Override
    		public void run() {
    			System.out.println("thread1");
    			
    		}
    	});
    	static Thread thread2 =new Thread(new Runnable() {
    		@Override
    		public void run() {
    			System.out.println("thread2");
    			
    		}
    	});
    	static Thread thread3 =new Thread(new Runnable() {
    		@Override
    		public void run() {
    			System.out.println("thread3");
    			
    		}
    	});
    	public static void main(String[] args) throws InterruptedException {
    		thread1.start();
    		thread1.join();
    		thread2.start();
    		thread2.join();
    		thread3.start();
    	}

由于直接调用join()方法时，底层调用的为Object的wait方法.

> ### ** 2.ExecutorService executor =  Executors.newSingleThreadExecutor();** ###

static Thread thread1 =new Thread(new Runnable() {
    		@Override
    		public void run() {
    			System.out.println("thread1");
    			
    		}
    	});
    	static Thread thread2 =new Thread(new Runnable() {
    		@Override
    		public void run() {
    			System.out.println("thread2");
    			
    		}
    	});
    	static Thread thread3 =new Thread(new Runnable() {
    		@Override
    		public void run() {
    			System.out.println("thread3");
    			
    		}
    	});
    	public static void main(String[] args) {
    		ExecutorService executor =  Executors.newSingleThreadExecutor();
    		executor.submit(thread1);
    		executor.submit(thread2);
    		executor.submit(thread3);
    	}

利用并发包里的Excutors的newSingleThreadExecutor产生一个单线程的线程池，而这个线程池的底层原理就是一个先进先出（FIFO）的队列。代码中executor.submit依次添加了123线程，按照FIFO的特性，执行顺序也就是123的执行结果，从而保证了执行顺序 。注:该方法在JDK1.5之后才引入