Fork/Join框架介绍

下面使用该框架计算0-50000000000的和，并比较普通计算方法、Fork/Join框架、Java8新特性三种计算方式的计算时间：

1 import java.time.Duration; 2 import java.time.Instant; 3 import java.util.concurrent.ForkJoinPool; 4 import java.util.concurrent.ForkJoinTask; 5 import java.util.concurrent.RecursiveTask; 6 import java.util.stream.LongStream; 7  8 import org.junit.Test; 9 10 public class TestForkJoinPool {11 12     public static void main(String[] args) {13         Instant start = Instant.now();14         ForkJoinPool pool = new ForkJoinPool();15         ForkJoinTask
     
       task = new ForkJoinSumCalculate(0L, 50000000000L);16         Long sum = pool.invoke(task);17         System.out.println(sum);18         Instant end = Instant.now();19         System.out.println("耗费时间为：" + Duration.between(start, end).toMillis());//1059020     }21 22     @Test23     public void test1(){24         Instant start = Instant.now();25         long sum = 0L;26         for (long i = 0L; i <= 50000000000L; i++) {27             sum += i;28         }29         System.out.println(sum);30         Instant end = Instant.now();31         System.out.println("耗费时间为：" + Duration.between(start, end).toMillis());//1570432     }33 34     //java8 新特性35     @Test36     public void test2(){37         Instant start = Instant.now();38         Long sum = LongStream.rangeClosed(0L, 50000000000L)39                              .parallel()40                              .reduce(0L, Long::sum);41         System.out.println(sum);42         Instant end = Instant.now();43         System.out.println("耗费时间为：" + Duration.between(start, end).toMillis());//811844     }45 }46 47 class ForkJoinSumCalculate extends RecursiveTask
      
       {48 49     private static final long serialVersionUID = -259195479995561737L;50     51     private long start;52     private long end;53     private static final long THURSHOLD = 10000L;  //临界值54     public ForkJoinSumCalculate(long start, long end) {55         this.start = start;56         this.end = end;57     }58 59     @Override60     protected Long compute() {61         long length = end - start;62         if(length <= THURSHOLD){63             long sum = 0L;64             for (long i = start; i <= end; i++) {65                 sum += i;66             }67             return sum;68         }else{69             long middle = (start + end) / 2;70             ForkJoinSumCalculate left = new ForkJoinSumCalculate(start, middle); 71             left.fork(); //进行拆分，同时压入线程队列72             ForkJoinSumCalculate right = new ForkJoinSumCalculate(middle+1, end);73             right.fork(); //74             return left.join() + right.join();75         }76     }77 }
      
     

 转载自：http://blog.csdn.net/xiangwanpeng/article/details/54977709