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本文主要研究一下线程池的预热

prestartCoreThread

java/util/concurrent/ThreadPoolExecutor.java

    /**
     * Starts a core thread, causing it to idly wait for work. This
     * overrides the default policy of starting core threads only when
     * new tasks are executed. This method will return {@code false}
     * if all core threads have already been started.
     *
     * @return {@code true} if a thread was started
     */
    public boolean prestartCoreThread() {
        return workerCountOf(ctl.get()) < corePoolSize &&
            addWorker(null, true);
    }

ThreadPoolExecutor定义了prestartCoreThread，用于启动一个核心线程

prestartAllCoreThreads

java/util/concurrent/ThreadPoolExecutor.java

    /**
     * Starts all core threads, causing them to idly wait for work. This
     * overrides the default policy of starting core threads only when
     * new tasks are executed.
     *
     * @return the number of threads started
     */
    public int prestartAllCoreThreads() {
        int n = 0;
        while (addWorker(null, true))
            ++n;
        return n;
    }

prestartAllCoreThreads用于启动所有的核心线程

小结

ThreadPoolExecutor提供了prestartCoreThread方法，用于启动一个核心线程，提供了prestartAllCoreThreads方法用于启动所有的核心线程。