Java中四种线程池介绍

心已赠人 2021-09-24 05:32 375阅读 0赞

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Java里面线程池的顶级接口是Executor，但是严格意义上讲Executor并不是一个线程池，而是一个执行线程的工具。真正的线程池接口是ExecutorService.

1.newCachedThreadPool

为每一个任务创建一个线程，并且可以重用已有的线程，无核心线程数量，超过60s的空闲线程将会被启用

/\*\*无参构造方法\*/  
 public static ExecutorService newCachedThreadPool() \{  
        return new ThreadPoolExecutor(0, Integer.MAX\_VALUE,  
                                      60L, TimeUnit.SECONDS,  
                                      new SynchronousQueue<Runnable>());  
    \}  
 /\*\*有参的构造方法，可以传入threadFactory\*/  
 public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) \{  
        return new ThreadPoolExecutor(0, Integer.MAX\_VALUE,  
                                      60L, TimeUnit.SECONDS,  
                                      new SynchronousQueue<Runnable>(),  
                                      threadFactory);  
    \}  
2.newFixedThreadPool

核心线程数和最大线程数是相同的，无空闲线程，核心线程数无限时要求，可以创建固定大小的线程数量，阻塞队列没有大小限制

/\*\*创建固定大小的线程数\*/  
public static ExecutorService newFixedThreadPool(int nThreads) \{  
        return new ThreadPoolExecutor(nThreads, nThreads,  
                                      0L, TimeUnit.MILLISECONDS,  
                                      new LinkedBlockingQueue<Runnable>());  
    \}  
   
/\*\*创建固定大小的线程数，并可以指定threadFactory\*/  
 public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) \{  
        return new ThreadPoolExecutor(nThreads, nThreads,  
                                      0L, TimeUnit.MILLISECONDS,  
                                      new LinkedBlockingQueue<Runnable>(),  
                                      threadFactory);

3.newScheduledThreadPool

延期和定时执行线程的线程池，固定的核心线程数，最大线程数没有限制，空闲的线程会立即启用

/\*\*创建固定大小的corePool\*/  
public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) \{  
        return new ScheduledThreadPoolExecutor(corePoolSize);  
    \}  
/\*\*查看ScheduledThreadPoolExecutor类，发现是集成的ThreadPoolExecutor\*/  
 public ScheduledThreadPoolExecutor(int corePoolSize) \{  
        super(corePoolSize, Integer.MAX\_VALUE, 0, NANOSECONDS,  
              new DelayedWorkQueue());  
    \}  
/\*\*创建固定大小的corePool,并指定threadFactory\*/  
 public static ScheduledExecutorService newScheduledThreadPool(  
            int corePoolSize, ThreadFactory threadFactory) \{  
        return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);  
    \}  
/\*\*查看ScheduledThreadPoolExecutor类，发现是集成的ThreadPoolExecutor\*/  
 public ScheduledThreadPoolExecutor(int corePoolSize,  
                                       ThreadFactory threadFactory) \{  
        super(corePoolSize, Integer.MAX\_VALUE, 0, NANOSECONDS,  
              new DelayedWorkQueue(), threadFactory);

4.newSingleThreadExecutor

创建只有一个的核心线程，只处理一个线程，不能处理并发

/\*\*无参\*/  
public static ExecutorService newSingleThreadExecutor() \{  
    return new FinalizableDelegatedExecutorService  
        (new ThreadPoolExecutor(1, 1,  
                                0L, TimeUnit.MILLISECONDS,  
                                new LinkedBlockingQueue<Runnable>()));  
\}  
/\*\*指定threadFactory\*/  
public static ScheduledExecutorService newSingleThreadScheduledExecutor(ThreadFactory threadFactory) \{  
        return new DelegatedScheduledExecutorService  
            (new ScheduledThreadPoolExecutor(1, threadFactory));

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