public final boolean isAlive()
Tests if this thread is alive. A thread is alive if it has been started and has not yet died.
Returns:
true if this thread is alive; false otherwise.

package soarhu;

import java.util.concurrent.TimeUnit;

/**
 * Created by huaox on 2017/4/17.
 *
 */

class ThreadTest extends Thread{

    private int count = 5;


    @Override
    public  void run() {
        System.out.println("3->"+Thread.currentThread().isAlive());
    }

}

public class Test {
    public static void main(String[] args) throws InterruptedException {
        ThreadTest thread = new ThreadTest();
        thread.setName("a");
        System.out.println("1->"+thread.isAlive());
        thread.start();
        TimeUnit.SECONDS.sleep(3);
        System.out.println("2->"+thread.isAlive());
    }
}

public static void sleep(long millis)
                  throws InterruptedException
Causes the currently executing thread to sleep (temporarily cease execution) for the specified number of milliseconds,
 subject to the precision and accuracy of system timers and schedulers.
 The thread does not lose ownership of any monitors. // 线程休眠后不会丢掉它的所属监视器，即如果有锁则不会释放锁。
Parameters:
millis - the length of time to sleep in milliseconds
Throws:
IllegalArgumentException - if the value of millis is negative
InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.
//当休眠的线程被中断时，sleep（）方法则会抛出InterruptedException.例如调用该线程的interrupt（）方法，那么该异常将被抛出并且线程的中断状态将会被清除，

package soarhu;

/**
 * Created by huaox on 2017/4/17.
 *
 */

class ThreadTest extends Thread{

    private long count = 20;


    @Override
    public synchronized void run() {
        count<<=1;
        System.out.println("run: "+count);
    }

    synchronized void second(){ //和run方法的锁是同一个锁对象，
        try {
            count-=5;
            Thread.sleep(3000);
            System.out.println("second: "+count);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

}

public class Test {
    public static void main(String[] args) throws InterruptedException {
        ThreadTest thread = new ThreadTest();
        thread.start();
        thread.second();//该方法会先于thread的run方法执行
    }
}

package soarhu;

import java.util.concurrent.TimeUnit;

/**
 * Created by huaox on 2017/4/17.
 *
 */
class ThreadTest extends Thread{
    private long count = 20;
    @Override
    public  void run() {
        count<<=1;
        try {
            System.out.println("sleep before: "+Thread.currentThread().isInterrupted());
            TimeUnit.SECONDS.sleep(10);//收到interrupt(）时，会触发中断异常，并且将中断状态设置为true.
        } catch (InterruptedException e) {
            System.out.println("catch: "+Thread.currentThread().isInterrupted());//carch块中，中断状态将被清除。设置为false
            e.printStackTrace();
        }
    }
}
public class Test {
    public static void main(String[] args) throws InterruptedException {
        ThreadTest thread = new ThreadTest();
        thread.start();
        Thread.sleep(2000);
        thread.interrupt();//给线程发一个中断标志
        System.out.println("main: "+thread.isInterrupted());
    }
}

public void interrupt()
Interrupts this thread.
Unless the current thread is interrupting itself, which is always permitted, the checkAccess method of this thread is invoked,
which may cause a SecurityException to be thrown.如果当前线程没有中断它自己（这在任何情况下都是允许的），则该线程的 checkAccess 方法就会被调用，这可能抛出 SecurityException。
If this thread is blocked in an invocation of the wait(), wait(long), or wait(long, int) methods of the Object class,
   or of the join(), join(long), join(long, int), sleep(long), or sleep(long, int), methods of this class,
   then its interrupt status will be cleared and it will receive an InterruptedException.
If this thread is blocked in an I/O operation upon an interruptible channel 
   then the channel will be closed, the thread‘s interrupt status will be set,
   and the thread will receive a ClosedByInterruptException.
If this thread is blocked in a Selector then the thread‘s interrupt status will be set 
   and it will return immediately from the selection operation, possibly with a non-zero value, just as if the selector‘s wakeup method were invoked.
If none of the previous conditions hold then this thread‘s interrupt status will be set.
Interrupting a thread that is not alive need not have any effect.
Throws:
SecurityException - if the current thread cannot modify this thread

public static boolean interrupted()
Tests whether the current thread has been interrupted. The interrupted status of the thread is cleared by this method. //测试当前线程是否被中断，调用此方法会清除中断状态。
In other words, if this method were to be called twice in succession,
the second call would return false (unless the current thread were interrupted again, 
after the first call had cleared its interrupted status and before the second call had examined it).//调用两次该方法会返回false
A thread interruption ignored because a thread was not alive at the time of the interrupt will be reflected by this method returning false.

Returns:
true if the current thread has been interrupted; false otherwise.
See Also:
isInterrupted()

public boolean isInterrupted()
Tests whether this thread has been interrupted. The interrupted status of the thread is unaffected by this method.//调用该方法不会清除中断状态
A thread interruption ignored because a thread was not alive at the time of the interrupt will be reflected by this method returning false.

Returns:
true if this thread has been interrupted; false otherwise.
See Also:
interrupted()