if (command == null) thrownewNullPointerException(); /* * 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. */ intc= ctl.get(); if (workerCountOf(c) < corePoolSize) { if (addWorker(command, true)) return; c = ctl.get(); } if (isRunning(c) && workQueue.offer(command)) { intrecheck= ctl.get(); if (! isRunning(recheck) && remove(command)) reject(command); elseif (workerCountOf(recheck) == 0) addWorker(null, false); } elseif (!addWorker(command, false)) reject(command); }
privatefinalclassWorker extendsAbstractQueuedSynchronizer implementsRunnable { /** * This class will never be serialized, but we provide a * serialVersionUID to suppress a javac warning. */ privatestaticfinallongserialVersionUID=6138294804551838833L;
/** Thread this worker is running in. Null if factory fails. */ final Thread thread; /** Initial task to run. Possibly null. */ Runnable firstTask; /** Per-thread task counter */ volatilelong completedTasks;
/** * Creates with given first task and thread from ThreadFactory. * @param firstTask the first task (null if none) */ Worker(Runnable firstTask) { setState(-1); // inhibit interrupts until runWorker this.firstTask = firstTask; this.thread = getThreadFactory().newThread(this); }
/** Delegates main run loop to outer runWorker */ // 启动线程 Worker publicvoidrun() { runWorker(this); }
privatevoidprocessWorkerExit(Worker w, boolean completedAbruptly) { if (completedAbruptly) // If abrupt, then workerCount wasn't adjusted decrementWorkerCount();