Java线程池总结

public ThreadPoolExecutor(
   int corePoolSize,
   int maximumPoolSize,                              
       long keepAliveTime,
    TimeUnit unit,
    BlockingQueue<Runnable> workQueue,
    ThreadFactory threadFactory,
    RejectedExecutionHandler handler){
}

new ThreadFactoryBuilder().setNameFormat("XX-task-%d").build();

threadsPool.execute(new Runnable() {
    @Override
public void run() {
// TODO Auto-generated method stub
}
});

Future<Object> future = executor.submit(haveReturnValuetask);
try {
Object s = future.get();
} catch (InterruptedException e) {
// 处理中断异常
} catch (ExecutionException e) {
// 处理无法执行任务异常
} finally {
// 关闭线程池
executor.shutdown();
}

static BlockingQueue blockingQueue=new ArrayBlockingQueue<>(1);
static ThreadPoolExecutor threadPoolExecutor=new ThreadPoolExecutor(10, 20, 1, TimeUnit.MINUTES, blockingQueue);

static class TaskBusyWithoutResult implements Runnable
{
    public TaskBusyWithoutResult()
    {
    }
    @Override
    public void run() 
    {
        System.out.println("线程"+Thread.currentThread()+"开始运行");
        int i=10000*10000;
        while(i>0)
        {
            i--;
        }
        System.out.println("线程"+Thread.currentThread()+"运行结束");
    }
}

public static void main(String[] args) {
    for (int i = 0; i < 20; i++) {
        Runnable runnable = new TaskBusyWithoutResult();
        threadPoolExecutor.submit(runnable);
    }
}

private final AtomicInteger ctl = new AtomicInteger(ctlOf(RUNNING, 0));
    private static final int COUNT_BITS = Integer.SIZE - 3;
    private static final int CAPACITY   = (1 << COUNT_BITS) - 1;
 
    // runState is stored in the high-order bits
    private static final int RUNNING    = -1 << COUNT_BITS;
    private static final int SHUTDOWN   =  0 << COUNT_BITS;
    private static final int STOP       =  1 << COUNT_BITS;
    private static final int TIDYING    =  2 << COUNT_BITS;
    private static final int TERMINATED =  3 << COUNT_BITS;
 
    // Packing and unpacking ctl
    private static int runStateOf(int c)     { return c & ~CAPACITY; }
    private static int workerCountOf(int c)  { return c & CAPACITY; }
    private static int ctlOf(int rs, int wc) { return rs | wc; }

public void execute(Runnable command) {
    //如果提交了空的任务 抛出异常
  if (command == null)
    throw new NullPointerException();
  int c = ctl.get();//获取当前线程池的状态
    //检查当前工作线程数量是否小于核心线程数量
  if (workerCountOf(c) < corePoolSize) {
    //通过addWorker方法提交任务
    if (addWorker(command, true))
      return;
    c = ctl.get();//如果提交失败 需要二次检查状态
  }
  //向工作线程提交任务 
  if (isRunning(c) && workQueue.offer(command)) {
    // 再次检查状态
       int recheck = ctl.get();
       
       if (! isRunning(recheck) && remove(command))
         reject(command);
       else if (workerCountOf(recheck) == 0)
         addWorker(null, false);
  }
  //扩容失败 则拒绝任务
  else if (!addWorker(command, false))
    reject(command);
}

private boolean addWorker(Runnable firstTask, boolean core) {
        retry:
    //死循环更新状态
        for (;;) {
            int c = ctl.get();
            int rs = runStateOf(c);//获取运行状态
 
        //检查线程池是否处于关闭状态
            if (rs >= SHUTDOWN &&
                ! (rs == SHUTDOWN &&
                   firstTask == null &&
                   ! workQueue.isEmpty()))
                return false;
    
            for (;;) {
          //获取当前工作线程数量
                int wc = workerCountOf(c);
        //如果已经超过corePoolSize获取maximumPoolSize 返回false
                if (wc >= CAPACITY ||
                    wc >= (core ? corePoolSize : maximumPoolSize))
                    return false;
        //CAS增加一个工作线程
                if (compareAndIncrementWorkerCount(c))
                 break retry;
        //再次获取状态
                c = ctl.get();  // Re-read ctl
        //如果状态更新失败 则循环更新
                if (runStateOf(c) != rs)
                    continue retry;
                // else CAS failed due to workerCount change; retry inner loop
            }
        }
 
        boolean workerStarted = false;
        boolean workerAdded = false;
        Worker w = null;
        try {
            w = new Worker(firstTask);//初始化一个工作线程
            final Thread t = w.thread;
            if (t != null) {
         //获得锁
                final ReentrantLock mainLock = this.mainLock;
                mainLock.lock();
                try {
                    // Recheck while holding lock.
                    // Back out on ThreadFactory failure or if
                    // shut down before lock acquired.
                    int rs = runStateOf(ctl.get());
 
                    if (rs < SHUTDOWN ||
                        (rs == SHUTDOWN && firstTask == null)) {
                        if (t.isAlive()) // precheck that t is startable
                            throw new IllegalThreadStateException();
            //添加工作这到hashset中保存
                        workers.add(w);
                        int s = workers.size();
                        if (s > largestPoolSize)
                            largestPoolSize = s;
                        workerAdded = true;
                    }
                } finally {
                    mainLock.unlock();
                }
                if (workerAdded) {
        //工作线程启动 执行第一个任务 就是新提交的任务
                    t.start();
                    workerStarted = true;
                }
            }
        } finally {
            if (! workerStarted)
                addWorkerFailed(w);
        }
        return workerStarted;
    }

/**
 * 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  */
public void run() {
     ‍runWorker(this);
}

final void runWorker(Worker w) {
        
     ‍Thread wt = Thread.currentThread();
     ‍Runnable task = w.firstTask;
     ‍w.firstTask = null;
     ‍w.unlock(); // allow interrupts
     ‍boolean completedAbruptly = true;
 ‍       ‍try {
        //不断地从blockingQueue获取任务
            while (task != null || (task = getTask()) != null) {
                w.lock();
                // If pool is stopping, ensure thread is interrupted;
                // if not, ensure thread is not interrupted.  This
                // requires a recheck in second case to deal with
                // shutdownNow race while clearing interrupt
                if ((runStateAtLeast(ctl.get(), STOP) ||
                     (Thread.interrupted() &&
                      runStateAtLeast(ctl.get(), STOP))) &&
                    !wt.isInterrupted())
                    wt.interrupt();
                try {
            //执行beforeExecute方法
                    beforeExecute(wt, task);
                    Throwable thrown = null;
                    try {
            //调用Runable的run方法
                        task.run();
                    } catch (RuntimeException x) {
                        thrown = x; throw x;
                    } catch (Error x) {
                        thrown = x; throw x;
                    } catch (Throwable x) {
                        thrown = x; throw new Error(x);
                    } finally {
            // 执行aferExecute方法
                        afterExecute(task, thrown);
                    }
                } finally {
                    task = null;
                    w.completedTasks++;
                    w.unlock();
                }
            }
            completedAbruptly = false;
        } finally {
            processWorkerExit(w, completedAbruptly);
        }
}