Java並行ThreadPoolExecutor類

java.util.concurrent.ThreadPoolExecutor是一個ExecutorService，可以使用可能的幾個池執行緒來執行每個提交的任務，通常使用Executors工廠方法進行組態。 它還提供了各種實用方法來檢查當前執行緒統計資訊並進行控制。

範例

以下TestThread程式顯示線上程環境中ThreadPoolExecutor介面的使用。

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 {
      ThreadPoolExecutor executor = (ThreadPoolExecutor)Executors.newCachedThreadPool();

      //Stats before tasks execution
      System.out.println("Core threads: " + executor.getCorePoolSize());
      System.out.println("Largest executions: "
         + executor.getLargestPoolSize());
      System.out.println("Maximum allowed threads: "
         + executor.getMaximumPoolSize());
      System.out.println("Current threads in pool: "
         + executor.getPoolSize());
      System.out.println("Currently executing threads: "
         + executor.getActiveCount());
      System.out.println("Total number of threads(ever scheduled): "
         + executor.getTaskCount());

      executor.submit(new Task());
      executor.submit(new Task());

      //Stats after tasks execution
      System.out.println("Core threads: " + executor.getCorePoolSize());
      System.out.println("Largest executions: "
         + executor.getLargestPoolSize());
      System.out.println("Maximum allowed threads: "
         + executor.getMaximumPoolSize());
      System.out.println("Current threads in pool: "
         + executor.getPoolSize());
      System.out.println("Currently executing threads: "
         + executor.getActiveCount());
      System.out.println("Total number of threads(ever scheduled): "
         + executor.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();
         }
      }
   }
}

執行上面程式，得到以下結果 -

Core threads: 0
Largest executions: 0
Maximum allowed threads: 2147483647
Current threads in pool: 0
Currently executing threads: 0
Total number of threads(ever scheduled): 0
Core threads: 0
Largest executions: 2
Maximum allowed threads: 2147483647
Current threads in pool: 2
Currently executing threads: 2
Total number of threads(ever scheduled): 2
Running Task! Thread Name: pool-1-thread-1
Running Task! Thread Name: pool-1-thread-2
Task Completed! Thread Name: pool-1-thread-2
Task Completed! Thread Name: pool-1-thread-1