求高手：看看简单代码的问题

import java.util.concurrent.TimeUnit;  

import java.util.concurrent.locks.Lock;  

import java.util.concurrent.locks.ReentrantLock; 

import java.util.concurrent.locks.Condition; 



class B

{

        Lock lock=new ReentrantLock();

        Condition con=lock.newCondition();

        void f()

        {

                lock.lock();

                System.out.print(Thread.currentThread().getName());

                System.out.println(">>I'm running");

                try { con.await(); }

                catch(InterruptedException ex)

                {

                        System.out.print(Thread.currentThread().getName());

                        System.out.println(">>I'm interrupted!");

                }

                System.out.print(Thread.currentThread().getName()); 

                System.out.println(">>exit!");

        }

}



class A extends Thread

{

        B b;

        A(B b){this.b=b;}

        public void run()

        {

               b.f();

        }

}



public class Test 

{  

    public static void main(String[] args)

    {

            B b=new B();  

            A a=new A(b);

            a.start();

            A aa=new A(b);

            aa.start();

            try{Thread.sleep(1000);}

            catch(InterruptedException ex){/*Deal with it!*/}

            a.interrupt();

            aa.interrupt();

    }  

}  

 

为什么a或aa线程其中有一个不能中断？
想不通问题出在哪儿，求高手！！
API docs：
The lock associated with this Condition is atomically released and the current thread becomes disabled for thread scheduling purposes and lies dormant until one of four things happens:

Some other thread invokes the signal() method for this Condition and the current thread happens to be chosen as the thread to be awakened; or
Some other thread invokes the signalAll() method for this Condition; or
Some other thread interrupts the current thread, and interruption of thread suspension is supported; or
A "spurious wakeup" occurs.

In all cases, before this method can return the current thread must re-acquire the lock associated with this condition. When the thread returns it is guaranteed to hold this lock.

If the current thread:

has its interrupted status set on entry to this method; or
is interrupted while waiting and interruption of thread suspension is supported,

then InterruptedException is thrown and the current thread's interrupted status is cleared. It is not specified, in the first case, whether or not the test for interruption occurs before the lock is released.

最后一句话（红色高亮）不是很理解，意思是不是如果在进入await方法时已经设置了中断状态，该方法是否抛出异常与实现有关。。。