30_请描述线程的生命周期

一图胜千言！

上述的图有些简略，下面详细说明下，线程共有6种状态：

new，runnable，blocked，waiting，timed waiting，terminated

1，当进入synchronized同步代码块或同步方法时，且没有获取到锁，线程就进入了blocked状态，直到锁被释放，重新进入runnable状态

2，当线程调用wait()或者join时，线程都会进入到waiting状态，当调用notify或notifyAll时，或者join的线程执行结束后，会进入runnable状态

3，当线程调用sleep(time)，或者wait(time)时，进入timed waiting状态，

当休眠时间结束后，或者调用notify或notifyAll时会重新runnable状态。

4，程序执行结束，线程进入terminated状态

 

案例篇

/**
 * @author huangguizhao
 * 测试线程的状态
 */
public class ThreadStateTest {
    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(new Task());
        System.out.println(thread.getState());//NEW
        thread.start();
        System.out.println(thread.getState());//RUNNABLE
        //保险起见，让当前主线程休眠下
        Thread.sleep(10);
        System.out.println(thread.getState());//terminated
    }
}
class Task implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            System.out.println(i);
        }
    }
}

 

public class ThreadStateTest {
    public static void main(String[] args) throws InterruptedException {
        BlockTask task = new BlockTask();
        Thread t1 = new Thread(task);
        Thread t2 = new Thread(task);
        t1.start();
        t2.start();
        //从严谨的角度来说，t1线程不一定会先执行，此处是假设t1先执行
        System.out.println(t1.getState());//RUNNABLE
        System.out.println(t2.getState());//BLOCKED
        Thread.sleep(10);
        System.out.println(t1.getState());//TIMED_WAITING
        Thread.sleep(1000);
        System.out.println(t1.getState());//WAITING
    }
}

class BlockTask implements Runnable{

    @Override
    public void run() {
        synchronized (this){
            //另一个线程会进入block状态
            try {
                //目的是让线程进入waiting time状态
                Thread.sleep(1000);
                //进入waiting状态
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

注意：

blocked，waiting，timed waiting 我们都称为阻塞状态

上述的就绪状态和运行状态，都表现为runnable状态