【转】Fork/Join框架测试

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：

 import java.time.Duration;
 import java.time.Instant;
 import java.util.concurrent.ForkJoinPool;
 import java.util.concurrent.ForkJoinTask;
 import java.util.concurrent.RecursiveTask;
 import java.util.stream.LongStream;

 import org.junit.Test;

 public class TestForkJoinPool {

     public static void main(String[] args) {
         Instant start = Instant.now();
         ForkJoinPool pool = new ForkJoinPool();
         ForkJoinTask<Long> task = new ForkJoinSumCalculate(0L, 50000000000L);
         Long sum = pool.invoke(task);
         System.out.println(sum);
         Instant end = Instant.now();
         System.out.println("耗费时间为：" + Duration.between(start, end).toMillis());//
     }

     @Test
     public void test1(){
         Instant start = Instant.now();
         long sum = 0L;
         for (long i = 0L; i <= 50000000000L; i++) {
             sum += i;
         }
         System.out.println(sum);
         Instant end = Instant.now();
         System.out.println("耗费时间为：" + Duration.between(start, end).toMillis());//
     }

     //java8 新特性
     @Test
     public void test2(){
         Instant start = Instant.now();
         Long sum = LongStream.rangeClosed(0L, 50000000000L)
                              .parallel()
                              .reduce(0L, Long::sum);
         System.out.println(sum);
         Instant end = Instant.now();
         System.out.println("耗费时间为：" + Duration.between(start, end).toMillis());//
     }
 }

 class ForkJoinSumCalculate extends RecursiveTask<Long>{

     private static final long serialVersionUID = -259195479995561737L;

     private long start;
     private long end;
     private static final long THURSHOLD = 10000L;  //临界值
     public ForkJoinSumCalculate(long start, long end) {
         this.start = start;
         this.end = end;
     }

     @Override
     protected Long compute() {
         long length = end - start;
         if(length <= THURSHOLD){
             long sum = 0L;
             for (long i = start; i <= end; i++) {
                 sum += i;
             }
             return sum;
         }else{
             long middle = (start + end) / 2;
             ForkJoinSumCalculate left = new ForkJoinSumCalculate(start, middle);
             left.fork(); //进行拆分，同时压入线程队列
             ForkJoinSumCalculate right = new ForkJoinSumCalculate(middle+1, end);
             right.fork(); //
             return left.join() + right.join();
         }
     }
 }

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