執行緒池以及四種常見執行緒池

執行緒池以及四種常見執行緒池

public ThreadPoolExecutor(int corePoolSize,//核心執行緒池大小，核心執行緒將會盡可能地一直活著
                          int maximumPoolSize,//執行緒池最大數量包括核心執行緒數量
                          long keepAliveTime,//非核心執行緒最長存活時間
                          TimeUnit unit,//keepAliveTime的單位
                          BlockingQueue<Runnable> workQueue,//等待執行緒的佇列
                          ThreadFactory threadFactory,//執行緒工程
                          RejectedExecutionHandler handler)//執行緒拒絕執行回撥
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四種常見的執行緒池：

• Executors.newCachedThreadPool()

  new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                                    60L, TimeUnit.SECONDS,
                                    new SynchronousQueue<Runnable>())
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• Executors.newFixedThreadPool(int nThreads)

  new ThreadPoolExecutor(nThreads, nThreads,
                                    0L, TimeUnit.MILLISECONDS,
                                    new LinkedBlockingQueue<Runnable>())
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• Executors.newScheduledThreadPool(int nCorepoolSize)

  public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
      return new ScheduledThreadPoolExecutor(corePoolSize);
  }
  
  //ScheduledThreadPoolExecutor():
  public ScheduledThreadPoolExecutor(int corePoolSize) {
      super(corePoolSize, Integer.MAX_VALUE,
            DEFAULT_KEEPALIVE_MILLIS, MILLISECONDS,
            new DelayedWorkQueue());
  }
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  ​

• Executors.newSingleThreadPool()

  public static ExecutorService newSingleThreadExecutor() {
      return new FinalizableDelegatedExecutorService
          (new ThreadPoolExecutor(1, 1,
                                  0L, TimeUnit.MILLISECONDS,
                                  new LinkedBlockingQueue<Runnable>()));
  }
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  ​