package com.test.testforkjoin;
import java.time.Duration;
import java.time.Instant;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;
import java.util.concurrent.RecursiveAction;
import java.util.concurrent.RecursiveTask;
/**
* @author Administrator
*/
public class ForkJoinCalculate extends RecursiveTask<Long> {
private static final long THRESHOLD = 10000;
private Long start;
private Long end;
public ForkJoinCalculate(Long start, Long end) {
this.start = start;
this.end = end;
}
@Override
protected Long compute() {
long sum = 0;
long length = end -start;
if (length < THRESHOLD) {
for (long i = start; i < end; i++) {
sum += i;
}
return sum;
} else {
long middle = (end + start)/2;
ForkJoinCalculate left = new ForkJoinCalculate(start,middle);
left.fork();
ForkJoinCalculate right = new ForkJoinCalculate(middle + 1, end);
right.fork();
return left.join() + right.join();
}
}
public static void main(String[] args) {
Instant start = Instant.now();
ForkJoinPool pool = new ForkJoinPool();
ForkJoinTask<Long> task = new ForkJoinCalculate(0L, 10000000000L);
Long sum = pool.invoke(task);
System.out.println(sum);
Instant end = Instant.now();
System.out.println(Duration.between(start, end).toMillis());
normal();
}
public static void normal() {
Long sum = 0L;
Instant start = Instant.now();
for (long i = 0; i < 10000000000L; i++) {
sum += i;
}
Instant end = Instant.now();
System.out.println(">>>>"+Duration.between(start, end).toMillis());
}
}
测试结果：
-5345475101129947011
1170
>>>>20258
