# 06-控制线程

参考了《疯狂java讲义》的提法，将如下内容归为控制线程。

## join

主线程join一个线程，那么主线程会阻塞直到join进来的线程执行完，主线程继续执行， join如果带超时时间的话，那么如果超时的话主线程也会不再等join进去的线程而继续执行.

join实际就是判断join进来的线程存活状态，如果活着就调用wait(0),如果带超时时间了的话，wait里边的时间会算出来

```java
while (isAlive()) {
    wait(0);
}
```

### API

* public final void join() throws InterruptedException
* public final synchronized void join(long millis, int nanos)
* public final synchronized void join(long millis)

### 例子

```java
public class Demo_02_06_1_join extends Thread {
    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println(this.getName() + "  " + i);
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Demo_02_06_1_join joinThread = new Demo_02_06_1_join();
        for (int i = 0; i < 100; i++) {

            if (i == 10) {
                joinThread.start();
                joinThread.join();
            }
            // 打到9就停了，然后执行joinThread这里里边的代码，完事继续从10打
            System.out.println(Thread.currentThread().getName()+"  "+i);
        }
    }
}
```

## sleep

睡觉方法，使得线程暂停一段时间，进入阻塞状态。

### API

* public static native void sleep(long millis) throws InterruptedException
* public static void sleep(long millis, int nanos) throws InterruptedException

### 示例

```java
public class Demo_02_06_2_sleep extends Thread {
    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            if (i == 5) {
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
            // 输出到4停止， 5秒后继续
            System.out.println(this.getName() + "  " + i);
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Demo_02_06_2_sleep sleepThread = new Demo_02_06_2_sleep();
        sleepThread.start();
    }
}
```

## yield

也是让线程暂停一下，但是是进入就绪状态，让系统重新开始一次新的调度过程

```
Thread.yield()
```

## 中断

Java中断机制是一种协作机制，也就是说通过中断并不能直接终止另一个线程，而需要被中断的线程自己处理中断。

前面有一些方法声明了InterruptedException， 这意味者他们可以被中断，中断后把异常抛给调用方，让调用方自己处理.

被中断的线程可以自已处理中断，也可以不处理或者抛出去。

```java
public class Demo_02_06_3_interrupt extends Thread {

    static class MyCallable implements Callable {
        @Override
        public Integer call() throws InterruptedException {
            for (int i = 0; i < 5000; i++) {
                if (Thread.currentThread().isInterrupted()) {
                    System.out.println("3333");
                    throw new InterruptedException("中断我干嘛，关注 微信号 大雄和你一起学编程 呀");
                }
            }
            return 0;
        }
    }
    public static void main(String[] args) throws InterruptedException {
        FutureTask<Integer> futureTask = new FutureTask<>(new MyCallable());
        Thread thread = new Thread(futureTask);
        thread.start();
        for (int i = 0; i < 100; i++) {
            if (i == 3) {
                thread.interrupt();
            }
        }
        try {
            futureTask.get();
        } catch (ExecutionException e) {
            // 这里会捕获到异常
            e.printStackTrace();
        }

    }
}
```


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