Java類Executors詳解【待完善】

1.類簡介

 * Factory and utility methods for {@link Executor}, {@link
 * ExecutorService}, {@link ScheduledExecutorService}, {@link
 * ThreadFactory}, and {@link Callable} classes defined in this
 * package. This class supports the following kinds of methods:

針對定義在這個包中的 Executor，ExecutorService，ScheduledExecutorService ，ThreadFactory，Callable

• Methods that create and return an {@link ExecutorService} set up with commonly useful configuration settings. 使用常用且有用的配置去建立並返回一個 ExecutorService。

• Methods that create and return a {@link ScheduledExecutorService} set up with commonly useful configuration settings. 使用常用配置返回一個 ScheduledExecutorService

• Methods that create and return a “wrapped” ExecutorService, that disables reconfiguration by making implementation-specific methods inaccessible. 建立並返回一個"wrapped" ExecutorService，這使重配置無效，通過實現具體的，不可訪問的方法。

• Methods that create and return a {@link ThreadFactory} that sets newly created threads to a known state. 建立並返回一個ThreadFactory，這個可以設定最近建立的執行緒到一個指定的狀態。

• Methods that create and return a {@link Callable} out of other closure-like forms, so they can be used in execution methods requiring {@code Callable}.

2.方法介紹

• newFixedThreadPool

 /**
     * Creates a thread pool that reuses a fixed number of threads
     * operating off a shared unbounded queue.  At any point, at most
     * {@code nThreads} threads will be active processing tasks.
     * If additional tasks are submitted when all threads are active,
     * they will wait in the queue until a thread is available.
     * If any thread terminates due to a failure during execution
     * prior to shutdown, a new one will take its place if needed to
     * execute subsequent tasks.  The threads in the pool will exist
     * until it is explicitly {@link ExecutorService#shutdown shutdown}.
     *
     * @param nThreads the number of threads in the pool
     * @return the newly created thread pool
     * @throws IllegalArgumentException if {@code nThreads <= 0}
     */
    public static ExecutorService newFixedThreadPool(int nThreads) {
        return new ThreadPoolExecutor(nThreads, nThreads,
                                      0L, TimeUnit.MILLISECONDS,
                                      new LinkedBlockingQueue<Runnable>());
    }

該方法的功能就是：建立一個執行緒池，可用於複用一個固定數量的執行緒，操作一個共享的很大的（任務）佇列。