newFixedThreadPool方法

可以通过调用Executors类的静态newFixedThreadPool()方法来获取固定的线程池.

语法

ExecutorService fixedPool = Executors.newFixedThreadPool(2);

其中

• 最多2个线程将是处于活动状态以处理任务.

• 如果提交的线程超过2个，则它们将保留在队列中，直到线程可用.

• 如果线程在执行器执行关闭期间因故障而终止，则创建一个新线程取代它.

• 任何线程都存在，直到池关闭.

示例

以下TestThread程序在基于线程的环境中显示newFixedThreadPool方法的使用.

import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.ThreadPoolExecutor;import java.util.concurrent.TimeUnit;public class TestThread {   public static void main(final String[] arguments) throws InterruptedException {      ExecutorService executor = Executors.newFixedThreadPool(2);      // Cast the object to its class type      ThreadPoolExecutor pool = (ThreadPoolExecutor) executor;      //Stats before tasks execution      System.out.println("Largest executions: "         + pool.getLargestPoolSize());      System.out.println("Maximum allowed threads: "         + pool.getMaximumPoolSize());      System.out.println("Current threads in pool: "         + pool.getPoolSize());      System.out.println("Currently executing threads: "         + pool.getActiveCount());      System.out.println("Total number of threads(ever scheduled): "         + pool.getTaskCount());      executor.submit(new Task());      executor.submit(new Task());      //Stats after tasks execution      System.out.println("Core threads: " + pool.getCorePoolSize());      System.out.println("Largest executions: "         + pool.getLargestPoolSize());      System.out.println("Maximum allowed threads: "         + pool.getMaximumPoolSize());      System.out.println("Current threads in pool: "         + pool.getPoolSize());      System.out.println("Currently executing threads: "         + pool.getActiveCount());      System.out.println("Total number of threads(ever scheduled): "         + pool.getTaskCount());      executor.shutdown();   }     static class Task implements Runnable {      public void run() {                  try {            Long duration = (long) (Math.random() * 5);            System.out.println("Running Task! Thread Name: " +               Thread.currentThread().getName());               TimeUnit.SECONDS.sleep(duration);                        System.out.println("Task Completed! Thread Name: " +               Thread.currentThread().getName());         } catch (InterruptedException e) {            e.printStackTrace();         }      }   }}

这将产生以下结果.

输出

Largest executions: 0Maximum allowed threads: 2Current threads in pool: 0Currently executing threads: 0Total number of threads(ever scheduled): 0Core threads: 2Largest executions: 2Maximum allowed threads: 2Current threads in pool: 2Currently executing threads: 1Total number of threads(ever scheduled): 2Running Task! Thread Name: pool-1-thread-1Running Task! Thread Name: pool-1-thread-2Task Completed! Thread Name: pool-1-thread-2Task Completed! Thread Name: pool-1-thread-1