ForkJoinDemo
package com.xiaozhao.juc.forkjoin; import java.util.concurrent.RecursiveTask; /** * 如何使用forkjoin * 1.forkjoinPool 通过它来执行 * 2.计算任务forkjoinPool.execute(ForkjoinTask task) * 3.计算类需要继承ForkjoinTask */ public class ForkJoinDemo extends RecursiveTask<Long> { private Long start; private Long end; private Long temp = 10000L; public ForkJoinDemo(Long start, Long end) { this.start = start; this.end = end; } public void test(){ } @Override protected Long compute() { if((end-start) < temp){ Long sum = 0L; for (Long i = start; i <= end; i++) { sum += i; } // System.out.println(sum); return sum; }else { //分支合并计算 Long middle = (start+end) / 2; /** * 将任务拆分 */ ForkJoinDemo task1 = new ForkJoinDemo(start, middle); task1.fork();//将任务压入线程队列 ForkJoinDemo task2 = new ForkJoinDemo(middle+1,end); task2.fork();//将任务压入线程队列 Long result = task1.join()+task2.join(); return result; } } }Test
package com.xiaozhao.juc.forkjoin; import java.util.concurrent.ExecutionException; import java.util.concurrent.ForkJoinPool; import java.util.concurrent.ForkJoinTask; import java.util.stream.LongStream; public class Test { public static void main(String[] args) throws ExecutionException, InterruptedException { // test1();//执行计算1~10亿内求和，共花费时间:8770毫秒=====计算值：500000000500000000 // test2();//执行计算1~10亿内求和，共花费时间:7872毫秒=====计算值：500000000500000000 test3();//执行计算1~10亿内求和，共花费时间:538毫秒=====计算值：500000000500000000 } public static void test1(){ Long sum = 0L; long start = System.currentTimeMillis(); for (Long i = 1L; i <= 10_0000_0000; i++) { sum += i; } long end = System.currentTimeMillis(); System.out.println("执行计算1~10亿内求和，共花费时间:"+(end-start)+"毫秒"+"=====计算值："+sum); } public static void test2() throws ExecutionException, InterruptedException { long start = System.currentTimeMillis(); ForkJoinPool forkJoinPool = new ForkJoinPool(); ForkJoinTask<Long> task = new ForkJoinDemo(0L, 10_0000_0000L); ForkJoinTask<Long> submit = forkJoinPool.submit(task);//提交任务 Long sum = submit.get(); long end = System.currentTimeMillis(); System.out.println("执行计算1~10亿内求和，共花费时间:"+(end-start)+"毫秒"+"=====计算值："+sum); } public static void test3(){ long start = System.currentTimeMillis(); //stream并行流 long sum = LongStream.rangeClosed(0L, 10_0000_0000L).parallel().reduce(0, Long::sum); long end = System.currentTimeMillis(); System.out.println("执行计算1~10亿内求和，共花费时间:"+(end-start)+"毫秒"+"=====计算值："+sum); } }
