多线程概念与编程

一、多线程的生命周期：新建(New)、就绪（Runnable）、运行（Running）、阻塞(Blocked)和死亡(Dead)

1、新建状态：程序初始化一个Thread时，线程处于新建状态

2、就绪状态：线程Thread调用start()方法时，线程进入绪队列，等待调度运行

3、运行状态：线程获取CPU，运行run()或call()

4、堵塞状态：线程失去CPU，被挂起

5、死亡状态：线程正常运行结束或者异常退出，则线程消亡了

     

注意：suspend()、resume()、stop()这三个方法为废用方法，不推荐使用

 

二、多线程的三种实现方法

1、继承Thread类

public class MyThread extends Thread {@Overridepublic void run() {try {Thread.sleep(1000);System.out.println("我是Thread");} catch (InterruptedException e) {e.printStackTrace();}}public static void main(String[] args) {MyThread myThread = new MyThread();myThread.start();System.out.println("结束main");}}

2、实现Runnable接口

public class MyRunnable implements Runnable {@Overridepublic void run() {try {Thread.sleep(1000);System.out.println("我是runnable");} catch (InterruptedException e) {e.printStackTrace();}}public static void main(String[] args) {MyRunnable myRunnable = new MyRunnable();new Thread(myRunnable).start();System.out.println("结束main");}}

3、实现Callable接口

public class MyCallable implements Callable<Object> {@Overridepublic Object call() throws Exception {Thread.sleep(1000);System.out.println("我是Callabel");return "我是Callabel";}public static void main(String[] args) throws Exception {ExecutorService  pool = Executors.newCachedThreadPool();MyCallable myCallable = new MyCallable();pool.submit(myCallable);    
//        Future<Object> f = pool.submit(myCallable);
//        System.out.println(f.get().toString());    System.out.println("main结束");}
}

注：当用Future去接收call()返回值，该方法是阻塞的，即先打印“我是Callable”再打印“main结束”