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Java并發(fā)Futures和Callables類實例詳解

更新時間：2024年05月08日 09:52:42 作者：智慧浩海

Callable對象返回Future對象,該對象提供監(jiān)視線程執(zhí)行的任務(wù)進度的方法, Future對象可用于檢查Callable的狀態(tài),然后線程完成后從Callable中檢索結(jié)果,這篇文章給大家介紹Java并發(fā)Futures和Callables類的相關(guān)知識,感興趣的朋友一起看看吧

java.util.concurrent.Callable對象可以返回由線程完成的計算結(jié)果，而runnable接口只能運行線程。 Callable對象返回Future對象，該對象提供監(jiān)視線程執(zhí)行的任務(wù)進度的方法。 Future對象可用于檢查Callable的狀態(tài)，然后線程完成后從Callable中檢索結(jié)果。它還提供超時功能。

語法

//submit the callable using ThreadExecutor
//and get the result as a Future object
Future result10 = executor.submit(new FactorialService(10));
//get the result using get method of the Future object
//get method waits till the thread execution and then return the result of the execution. 
Long factorial10 = result10.get();

實例

以下TestThread程序顯示了基于線程的環(huán)境中Futures和Callables的使用。

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
public class TestThread {
   public static void main(final String[] arguments) throws InterruptedException, ExecutionException {
      ExecutorService executor = Executors.newSingleThreadExecutor();
      System.out.println("Factorial Service called for 10!");
      Future<Long> result10 = executor.submit(new FactorialService(10));
      System.out.println("Factorial Service called for 20!");
      Future<Long> result20 = executor.submit(new FactorialService(20));
      Long factorial10 = result10.get();
      System.out.println("10! = " + factorial10);
      Long factorial20 = result20.get();
      System.out.println("20! = " + factorial20);
      executor.shutdown();
   }  
   static class FactorialService implements Callable<Long>{
      private int number;
      public FactorialService(int number) {
         this.number = number;
      }
      @Override
      public Long call() throws Exception {
         return factorial();
      }
      private Long factorial() throws InterruptedException{
         long result = 1; 
         while (number != 0) { 
            result = number * result; 
            number--; 
            Thread.sleep(100); 
         } 
         return result;    
      }
   }
}

這將產(chǎn)生以下結(jié)果。