运行代码

package com.stream;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

/**
 * Created by lipei on 2017/8/26.
 *
 * 测试stream的效率
 *
 */
public class StreamTest {
    public static void main(String[] args) {

        System.out.println("for循环开始时间：" + LocalDateTime.now());

        long totalVal02 = 0;
        for(int i = 1; i<= 100; i++){
            totalVal02 += getNum(i);
        }

        System.out.println("totalNum = " + totalVal02);
        System.out.println("for循环结束时间：" + LocalDateTime.now());


        //串行
        System.out.println("Stream 开始时间：" + LocalDateTime.now());

        long totalVal01 =  Stream.iterate(1, n->n+1).limit(100).collect(Collectors.summingLong(StreamTest::getNum));

        System.out.println("totalNum = " + totalVal01);

        System.out.println("Stream 结束时间：" + LocalDateTime.now());



        //并行
        System.out.println("parallel Stream 开始时间：" + LocalDateTime.now());

        long totalVal03 =  Stream.iterate(1, n->n+1).limit(100).parallel().collect(Collectors.summingLong(StreamTest::getNum));

        System.out.println("totalNum = " + totalVal03);

        System.out.println("parallel Stream 结束时间：" + LocalDateTime.now());



    }

    public static long getNum(int m){
        Long totalNum = Long.valueOf(0);
        for(long i = 1; i <= 100000000l; i++){
            totalNum += m ;
        }
        return  totalNum;
    }
}

运行结果

for循环开始时间：2017-08-28T09:59:43.481
totalNum = 505000000000
for循环结束时间：2017-08-28T10:00:17.044

Stream 开始时间：2017-08-28T10:00:17.044
totalNum = 505000000000
Stream 结束时间：2017-08-28T10:00:50.738

parallel Stream 开始时间：2017-08-28T10:00:50.738
totalNum = 505000000000
parallel Stream 结束时间：2017-08-28T10:01:12.503

Process finished with exit code 0