Jdk源码详解之ThreadPoolExecutor 类

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Jdk源码详解之ThreadPoolExecutor 类

1.类释义

An ExecutorService that executes each submitted task using
one of possibly several pooled threads, normally configured
using  Executors factory methods.

一个ExecutorService（线程池），用于执行每个提交的任务，使用可用线程池的多个线程中的一个线程，常用的正常配置是：使用Excutors 的工厂方法。

2.类代码

ThreadPoolExecutor

public class ThreadPoolExecutor extends AbstractExecutorService {...}

3.主要方法

• 构造函数：ThreadPoolExecutor()

    /**
     Creates a new ThreadPoolExecutor with the given initial
     parameters and default rejected execution handler.
	 使用初始化参数，和默认的拒绝执行处理程序创建一个新的ThreadPoolExecutor。
     
     @param corePoolSize the number of threads to keep in the pool, even
            if they are idle, unless allowCoreThreadTimeOut is set
			留在线程池中的线程数，即使他们都是闲置的。除非allowCoreThreadTimeOut被设置。
			
     @param maximumPoolSize the maximum number of threads to allow in the
            pool
			允许留在线程池中的最大线程数
			
     @param keepAliveTime when the number of threads is greater than
            the core, this is the maximum time that excess idle threads
            will wait for new tasks before terminating.
			当线程数超过核数时，在等到新任务之前，这个时间是这些闲置线程会等待的最长时间
			
     @param unit the time unit for the {@code keepAliveTime} argument
				 keepAliveTime这个参数的单位
				 
     @param workQueue the queue to use for holding tasks before they are
            executed.  This queue will hold only the Runnable
            tasks submitted by the execute method.
			未执行任务的保存队列。这队列将会被保留，这个队列仅仅保存由execute()方法提交的任务。
			
     @param threadFactory the factory to use when the executor creates a new thread
			当executor创建一个新的进程时，会使用到的一个工厂
			
     @throws IllegalArgumentException if one of the following holds:<br>
             {@code corePoolSize < 0}<br>
             {@code keepAliveTime < 0}<br>
             {@code maximumPoolSize <= 0}<br>
             {@code maximumPoolSize < corePoolSize}
     @throws NullPointerException if {@code workQueue}
             or {@code threadFactory} is null
     */
    public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue<Runnable> workQueue,
                              ThreadFactory threadFactory) {
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
             threadFactory, defaultHandler);
    }

可以看到这里的BlockingQueue()是一个queue，用于保存即将执行的任务。这个 BlockingQueue接口的主要实现类有：ArrayBlockingQueue，

public class ArrayBlockingQueue<E> extends AbstractQueue<E>
        implements BlockingQueue<E>, java.io.Serializable {
        ...
        }

ArrayBlockingQueue类的释义如下：

A bounded BlockingQueue(blocking queue) backed by an array.
一个有界限的Blocking queue，底层是一个array。