这样受阻线程就得以退出阻塞的状态。更确切 的说,如果线程被Object.wait, Thread.join和Thread.sleep三种方法之一阻塞, 那么,它将接收到一个中断异常(InterruptedException),从而提早地终结被阻塞状态。
如果线程没有被阻塞,这时调用interrupt()将不起作用;否则,线程就将得到InterruptedException异常(该线程必须事先预备好处理此状况),接着逃离阻塞状态。
线程A在执行sleep,wait,join时,线程B调用线程A的interrupt方法,的确这一个时候A会有InterruptedException 异常抛出来.
但这其实是在sleep,wait,join这些方法内部会不断检查中断状态的值,而自己抛出的InterruptedException。
如果线程A正在执行一些指定的操作时如赋值,for,while,if,调用方法等,都不会去检查中断状态
,所以线程A不会抛出 InterruptedException,而会一直执行着自己的操作.
当线程A终于执行到wait(),sleep(),join()时,才马上会抛出 InterruptedException.
若没有调用sleep(),wait(),join()这些方法,即没有在线程里自己检查中断状态自己抛出InterruptedException的 话,
那InterruptedException是不会被抛出来的.
具体使用见实例1,实例2。
注意1:当线程A执行到wait(),sleep(),join()时,抛出InterruptedException后,中断状态已经被系统复位了,
线程A调用Thread.interrupted()返回的是false
public static boolean interrupted ()
Since: API Level 1
Returns a boolean
indicating whether the current Thread ( currentThread()
) has a pending interrupt
request ( true
) or not (false
). It also has the side-effect of clearing the flag.
Returns
-
a
boolean
indicating the interrupt status
public boolean isInterrupted ()
Since: API Level 1
Returns a boolean
indicating whether the receiver has a pending interrupt request (true
) or not ( false
)
Returns
-
a
boolean
indicating the interrupt status
线程A正在使用sleep()暂停着: Thread.sleep(100000);
如果要取消他的等待状态,可以在正在执行的线程里(比如这里是B)调用
a.interrupt();
令线程A放弃睡眠操作,这里a是线程A对应到的Thread实例
当在sleep中时 线程被调用interrupt()时,就马上会放弃暂停的状态.并抛出InterruptedException.丢出异常的,是A线程.
2. wait() & interrupt()
线程A调用了wait()进入了等待状态,也可以用interrupt()取消.
不过这时候要小心锁定的问题.线程在进入等待区,会把锁定解除,当对等待中的线程调用interrupt()时
,会先重新获取锁定,再抛出异常.在获取锁定之前,是无法抛出异常的.
3. join() & interrupt()
当线程以join()等待其他线程结束时,当它被调用interrupt(),它与sleep()时一样, 会马上跳到catch块里.
注意,是对谁调用interrupt()方法,一定是调用被阻塞线程的interrupt方法.如在线程a中调用来线程t.join().
则a会等t执行完后在执行t.join后的代码,当在线程b中调用来 a.interrupt()方法,则会抛出InterruptedException,当然join()也就被取消了。
实例1:
static void interruptDemo()
{
Thread t1=new Thread(new InterruptDemoRunnable(),"first");
Thread t2=new Thread(new InterruptDemoRunnable(t1),"second");
t1.start();
t2.start();
}
class InterruptDemoRunnable implements Runnable
{
long id=0;
static long count=0;
Thread t;
InterruptDemoRunnable()
{
this(null);
}
InterruptDemoRunnable(Thread t)
{
id=count++;
this.t=t;
}
boolean blRun=true;
public void run()
{ int cnt=0;
while(blRun)
{
if(t!=null)
{
if(cnt==2)
{
t.interrupt();
if(t.isInterrupted())
System.out.println("set the thread "+t.getName()+" to be Interrupted");
}
}
else
{
try
{
Thread.sleep(1000);
}
catch(InterruptedException e)
{
System.out.println("First Interrupted when sleep");
System.out.println( "Interrupted is "+Thread.interrupted());//@1
}
try
{
Thread.sleep(1);
}
catch(InterruptedException e)
{
System.out.println("second Interrupted when sleep");
}
}
System.out.println(id+"run"+cnt);
cnt++;
if(cnt==5)
{
blRun=false;
}
}
System.out.println("thread:"+id+"exit");
}
}
注意1:当线程A执行到wait(),sleep(),join()时,抛出InterruptedException后,中断状态已经被系统复位了。
线程AThread.interrupted()返回的是false
实例2:
static void interruptDemo()
{
Thread t1=new InterruptDemoThread();
t1.setName("t1");
Thread t2=new InterruptDemoThread(t1);
t1.setName("t2");
t1.start();
t2.start();
}
class InterruptDemoThread extends Thread
{
long id=0;
static long count=0;
Thread t;
InterruptDemoThread()
{
this(null);
}
InterruptDemoThread(Thread t)
{
id=count++;
this.t=t;
}
boolean blRun=true;
public void run()
{ int cnt=0;
while(blRun)
{
if(t!=null)
{
if(cnt==2)
{
t.interrupt();
if(t.isInterrupted())
System.out.println("set the thread "+t.getName()+" to be Interrupted");
}
}
else if(isInterrupted())@1
{
/*Thread.interrupted();//@2
System.out.println("after interrupted(),the state of Interrupted is "+isInterrupted());*/
try{
Thread.sleep(1);
}
catch(InterruptedException e)
{
System.out.println("Interrupted when sleep");
System.out.println( "Interrupted is "+Thread.interrupted());
}
}
Thread.yield();
System.out.println(id+"run"+cnt);
cnt++;
if(cnt==5)
{
blRun=false;
}
}
System.out.println("thread:"+id+"exit");
}
}
注意1:如果线程被调用了interrupt(),那么如果此次该线程并不在wait(),sleep(),join()时,
下次执行wait(),sleep(),join()时,一样会抛出InterruptedException,当然抛出后该线程的中断状态也回被系统复位。
注意2:我们可以手动的使用Thread.interrupted()来使当前线程的中断状态系统复位(即清除中断状态)
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