FutureTask源码学习

FutureTask源码

    FutureTask是一个可以用来监控Callable执行状况的类
    我们首先来看一下它是如何实现监控的:

 
     
     public void run() { 
        if (state != NEW || 
            !UNSAFE.compareAndSwapObject(this, runnerOffset, 
                                         null, Thread.currentThread())) 
            return; 
        try { 
            Callable c = callable; 
            if (c != null && state == NEW) { 
                V result; 
                boolean ran; 
                try { 
                    result = c.call(); 
                    ran = true; 
                } catch (Throwable ex) { 
                    result = null; 
                    ran = false; 
                    setException(ex); 
                } 
                if (ran) 
                    set(result); 
            } 
        } finally { 
            // runner must be non-null until state is settled to 
            // prevent concurrent calls to run() 
            runner = null; 
            // state must be re-read after nulling runner to prevent 
            // leaked interrupts 
            int s = state; 
            if (s >= INTERRUPTING) 
                handlePossibleCancellationInterrupt(s); 
        } 
    } 
     
    

    FutureTask覆盖了Runnable的run()方法，因此也算是一个线程，首先它获取callable，然后执行callable,然后修改callable的状态。根据callable的状态即可监控callable的状态。