Executor -->  ExecutorService  -->  AbstractExecutorService --> ThreadPoolExecuotorExecutor接口，只有一个execute方法，参数为线程任务ExecutorService接口继承Executor接口，增加了submit、shutdown、invokeAll等方法AbstractExecutorService抽象类，实现ExecutorService接口，提供了submit、invokeAny、invokeAll默认实现方法， execute、
shutdown、shutdownNow等待没有提供默认的实现ThreadPoolExecutor线程池状态值---RUNNING  接受新任务并且处理阻塞队列里的任务---SHUTDOWN  拒绝信任务但是处理阻塞队列里的任务---STOP  拒绝新任务并且抛弃阻塞队列里的任务同时会中断正在处理的任务---TIDYING  所有任务都执行完当前线程池活动线程为0，将调用terminated方法---TERMINATED  终止状态构造函数---有四个构造函数，其他三个都是调用下面这个构造函数public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit,BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) {}---参数说明corePoolSize  核心线程数maximumPoolSize  最大线程数keepAliveTime  存活时间unit  时间单位workQueue  存放线程的队列threadFactory  创建线程的工厂handler  拒绝策略提交任务---submitpublic Future<?> submit(Runable task) {if(task == null) throw new NullPointerException();RunnableFuture<Void> ftask = newTaskFor(task, null);execute(ftask);return ftask;}       public <T> Future<T> submit(Runnable task, T result) {if(task == null) throw new NullPointerExecetion();RunnableFuture<T> ftask = newTaskFor(task, result);execute(ftask);return ftask;}public <T> Future<T> submit(Callable<T> task) {if(task == null) throw new NullPointerException();RunnableFuture<T> ftask = newTaskFor(task);execute(ftask);return ftask;}--- executepublic void execute(Runnable command) {if(command == null) throw new NullPointerException();//获取当前线程池的状态+线程个数int c = ctl.get();//判断当前线程池数量是否小于corePoolSize，小于则调用addWorker方法创建新线程运行，且传进来的Runnable当做第一个任务执行if(workerCountOf(c) < corePoolSize) {if(addWorker(command, true))return;c = ctl.get();    }//如果线程池处于Running状态，则添加任务到阻塞队列if(isRunning(c) && workQueue.offer(command)) {int recheck = ctl.get();//如果当前线程池状态不是Running则从队列删除任务，并执行拒绝策略if(!isRunning(recheck) && remove(command))reject(command);//如果当前线程池为空，则添加一个线程    else if(workercountOf(recheck) == 0) addWorker(null, false);    }//新增线程失败则执行拒绝策略else if(!addWorker(command, false))reject(command);}---addWorkerprivate boolean addWorder(Runnable firstTask, boolean core) {retry:for(;;) {int c = ctl.get();int rs = runStateOf(c);//检查当前线程池状态是否是shutdown、stop、tidying、terminated且!(当前状态为shutdown、传入的任务为null、队列不为null),条件都成立时返回falseif (rs >= SHUTDOWN &&! (rs == SHUTDOWN &&firstTask == null &&! workQueue.isEmpty()))return false;for(;;) {int wc = workerCountOf(c);if(wc >= CAPACITY || wc >= (core ? corePoolSize : maximumPoolSize) )return false;if(compareAndIncrementWorkerCount(c))break retry;c = ctl.get();if(runStateOf(c) != rs) continue retry;    }}boolean workerStarted = false;boolean workerAdded = false;Worker w = null;try{// new threadw = new Worker(firstTask);final Thread t = w.thread();if(t != null) {//lockfinal ReentrantLock mainLock = this.mainLock;mainLock.lock();try{//check thread pool stateint rs = runStateOf(ctl.get());if(rs < SHUTDOWN || (rs == SHUTDOWN && firstTask == null) ) {//检查线程是否可启动if(t.isAlive())throw new IllegalThreadStateException();workers.add(w)   ;int s = workers.size();if(s > largestPoolSize)largestPoolSize = s;workerAdded = true;    } }finally {mainLock.unlock();}//判断worker是否添加成功，成功则启动线程，将workerStarted设置为trueif(workerAdded) {t.start();workerStarted = true;}}}finally{if(!workerStarted) addWorkerFailed(w);}return workerStarted;}---runWorker,线程启动时调用了runWorker方法final void runWorker(Worker w) {Thread wt = Thread.currentThread();Runnable task = w.firstTask;w.firstTask = null;w.unlock();boolean completedAbruptly = true;try {//循环获取任务while(task != null || (task = getTask()) != null ) {w.lock();// 当线程池是处于STOP状态或者TIDYING、TERMINATED状态时，设置当前线程处于中断状态// 如果不是，当前线程就处于RUNNING或者SHUTDOWN状态，确保当前线程不处于中断状态// 重新检查当前线程池的状态是否大于等于STOP状态if ((runStateAtLeast(ctl.get(), STOP) ||(Thread.interrupted() &&runStateAtLeast(ctl.get(), STOP))) &&!wt.isInterrupted())wt.interrupt();try {beforeExecute(wt, task);Throwable thrown = null;try {task.run();}catch(RuntimeException x) {thrown = x; throw x;}catch(Error x) {thrown = x; throw x;}catch(Throwable x) {thrown = x; throw Error(x);}finally {afterExecute(taskm thrown);}}finally {task = null;w.completedTasks++;w.unlock();} }completedAbruptly = false;}finally {processWokerExit(w, completedAbruptly);}}---getTaskprivate Runnable getTask() {boolean timeOut = false;for(;;) {int c = ctl.get();int rs = runStateOf(c);if(rs >= SHUTDOWN && (rs >= STOP || workQueue.isEmpty() )) {decrementWorkerCount();return null;}int wc = workerCountof(c);boolean timed = allowCoreThreadTimeOut || wc > corePoolSize;//（当前线程数是否大于最大线程数或者）//且（线程数大于1或者任务队列为空）//这里有个问题(timed && timedOut)timedOut = false，好像(timed && timedOut)一直都是false吧if ((wc > maximumPoolSize || (timed && timedOut))&& (wc > 1 || workQueue.isEmpty())) {if (compareAndDecrementWorkerCount(c))return null;continue;}try{Runnable r = timed ? workQueue.poll(keepAliveTime, TimeUnit.NANOSECONDS) : workQueue.take();if(r != null)return r;timedOut = true;    }catch(InterruptedException retry) {timedOut = false;}}}---shutdown 关闭线程池public void shutdown() {final ReentrantLock mainLock = this.mainLock;mainLock.lock();try{checkShutdownAccess();advanceRunState(SHUTDOWN);interruptIdleWorkers();onShutdown();}finally{mainLock.unlock();}tryTerminate();}