java 如何优雅的停止一个线程

写过多线程的童鞋，可能都会遇到一个问题，那就是线程如何优雅的停止。这里主要介绍两个办法：标志位 和 thread.isInterrupted。

1.通过 标志位 来终止线程

private static class Runner implements Runnable{
		private long i;
		private (volatile) boolean running =true;
		@Override
		public void run() {
			System.out.println("current Thread Name:"+Thread.currentThread().getName());
			while (running ){
				i++;
                try {
					TimeUnit.SECONDS.sleep(10);
				} catch (InterruptedException e) {
				}
			}
			System.out.println("Count i= "+i);
			System.out.println("current Thread Name:"+Thread.currentThread().getName());
			
		}
		public void cancel(){
			running =false;
			System.out.println("running=false");
		}
	}

此程序会在 running=false 之后，继续等待 10s ,通过 标识位 并不能阻止 sleep wait 等继续执行。
所以此方法不是特别优雅

2.通过 Thread.currentThread().isInterrupted() 来判断

public class Shutdoown {
	public static void main(String[] args) {
		Runner one = new Runner();
		Thread countThread = new Thread(one, "CountThread");
		countThread.start();
        try {
			//保证线程已启动
			TimeUnit.SECONDS.sleep(1);
		} catch (InterruptedException e) {
		}
		countThread.interrupt();
	}
	
	private static class Runner implements Runnable {
		private long i;
		private volatile boolean running = true;
		
		@Override
		public void run() {
			System.out.println("current Thread Name start:" + Thread.currentThread().getName());
			while (!Thread.currentThread().isInterrupted()) {
				System.out.println("=== " + Thread.currentThread().isInterrupted());
				i++;
				try {
					TimeUnit.SECONDS.sleep(5);
				} catch (InterruptedException e) {
					Thread.currentThread().interrupt();
					System.out.println("error=== " + e);
				}
			}
			System.out.println("Count i= " + i);
			System.out.println("current Thread Name stop:" + Thread.currentThread().getName());
			
		}
	}

thread 被中断之后，就可以无视 sleep wait 等方法，马上停止，乍一看，还是蛮优雅的，推荐使用。

可如果我把 sleep 换乘 while(true)会怎么样？

3. 通过 Thread.currentThread().isInterrupted() 来判断-while(true) 版本

public class Shutdoown {
	public static void main(String[] args) {
		Runner one = new Runner();
		Thread countThread = new Thread(one, "CountThread");
		countThread.start();
        try {
			//保证线程已启动
			TimeUnit.SECONDS.sleep(1);
		} catch (InterruptedException e) {
		}
		countThread.interrupt();
	}
	
	private static class Runner implements Runnable {
		private long i;
		private volatile boolean running = true;
		
		@Override
		public void run() {
			System.out.println("current Thread Name start:" + Thread.currentThread().getName());
			while (!Thread.currentThread().isInterrupted()) {
				System.out.println("=== " + Thread.currentThread().isInterrupted());
				i++;
				while(true){
                }
			}
			System.out.println("Count i= " + i);
			System.out.println("current Thread Name stop:" + Thread.currentThread().getName());
			
		}
	}

不要意思，除非主动 kill，不然 线程 永远停止不了。

总结：
显然，通过 Thread.currentThread().isInterrupted() 来停止线程，显然要比标示位优雅一些，但要防止条件判断永远无法生效。