[Java并发系列]Java中的线程池

public void execute(Runnable command) {        
         if (command == null)            
             throw new NullPointerException();        
         /*
         * Proceed in 3 steps:
         *
         * 1. If fewer than corePoolSize threads are running, try to
         * start a new thread with the given command as its first
         * task.  The call to addWorker atomically checks runState and
         * workerCount, and so prevents false alarms that would add
         * threads when it shouldn't, by returning false.
         *
         * 2. If a task can be successfully queued, then we still need
         * to double-check whether we should have added a thread
         * (because existing ones died since last checking) or that
         * the pool shut down since entry into this method. So we
         * recheck state and if necessary roll back the enqueuing if
         * stopped, or start a new thread if there are none.
         *
         * 3. If we cannot queue task, then we try to add a new
         * thread.  If it fails, we know we are shut down or saturated
         * and so reject the task.
         */
        int c = ctl.get();        
         //比较当前线程池中执行的线程数与核心线程池允许的最大线程数
        if (workerCountOf(c) < corePoolSize) {            
            if (addWorker(command, true))                
                return;
            c = ctl.get();
        }        
        if (isRunning(c) && workQueue.offer(command)) {            
            int recheck = ctl.get();            
            if (! isRunning(recheck) && remove(command))
                reject(command);            
            else if (workerCountOf(recheck) == 0)
                addWorker(null, false);
        }        
       else if (!addWorker(command, false))            
            reject(command);
    }

public ThreadPoolExecutor(int corePoolSize,                              
                              int maximumPoolSize,                              
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue<Runnable> workQueue,
                              ThreadFactory threadFactory,
                              RejectedExecutionHandler handler) {        
           if (corePoolSize < 0 || maximumPoolSize <= 0 ||
                    maximumPoolSize < corePoolSize ||keepAliveTime < 0)            
                throw new IllegalArgumentException();       
           if (workQueue == null || threadFactory == null || 
                    handler == null)            
               throw new NullPointerException();        
           this.corePoolSize = corePoolSize;        
           this.maximumPoolSize = maximumPoolSize;        
           this.workQueue = workQueue;        
           this.keepAliveTime = unit.toNanos(keepAliveTime);        
           this.threadFactory = threadFactory;        
           this.handler = handler;
    }