【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：
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<Long> 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());//10590 20 } 21 22 @Test 23 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());//15704 32 } 33 34 //java8 新特性 35 @Test 36 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());//8118 44 } 45 } 46 47 class ForkJoinSumCalculate extends RecursiveTask<Long>{ 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 @Override 60 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
