Java:Thread:join()

Java:Thread:join()方法加入一个线程

在Java多线程中，如果某一个线程s在另一个线程t上调用t.join()，此线程s将被挂起，直到目标线程t结束才恢复（此时t.isAlive()返回为假）。

也可以在调用join()时带上一个超时参数（单位可以是毫秒，或者毫秒和纳秒），这样如果目标线程在这段时间内还没有结束的话，join()方法总能返回。

对join()方法的调用可以被中断，做法是在调用线程上调用interrupt()方法。

class Sleeper extends Thread {

    private int duration;
    
    public Sleeper(String name, int sleepTime) {
        super(name);
        this.duration = sleepTime;
        start();
    }
    
    @Override
    public void run() {
        try {
            sleep(duration);
        } catch (InterruptedException e) {
            /** 异常被捕获时将清理线程的中断标识，因此在catch子句中isInterrupted()返回的值为false.*/
            System.out.println(getName() + "was interrupted. " + "isInterrupted(): " + isInterrupted());
            return ;
        }
        System.out.println(getName() + " has awakened.");
    }
    
}


class Joiner extends Thread {
    
    private Sleeper sleeper;
    
    public Joiner(String name, Sleeper sleeper) {
        super(name);
        this.sleeper = sleeper;
        start();
    }
    
    @Override
    public void run() {
        try {
            sleeper.join();
        } catch (InterruptedException e) {
            System.out.println("Interrupted.");
        }
        System.out.println(getName() + " join completed");
    }
    
}


public class JoinDemo {
    
    public static void main(String[] args) {
        Sleeper
            sleepy = new Sleeper("Sleepy", 1500),
            grumpy = new Sleeper("Grumpy", 1500);
        Joiner
            dopey = new Joiner("Dopey", sleepy),
            doc = new Joiner("Doc", grumpy);
        grumpy.interrupt();
    }

}

/**
 * 程序运行结果：
 * Grumpywas interrupted. isInterrupted(): false
 * Doc join completed
 * Sleepy has awakened.
 * Dopey join completed
 * 
 */