Steam学习

package jdk8steam;

import java.util.Objects;
import java.util.stream.Stream;

/**
 * Created by 80374563 on 2018/11/6.
 */
public class SteamParallel  {


    //顺序求和
    public static long sum(long n){
        Objects.requireNonNull(n);
        return Stream.iterate(1l,i -> i + 1)
                .limit(n)
                .reduce(0l,Long::sum);
    }

    //并行求和
    public static long parallelSum(long n){
        Objects.requireNonNull(n);
        return Stream.iterate(1l, i -> i + 1)
                .limit(n)
                //将流转为并行流
                .parallel()
                .reduce(0l, Long::sum);
    }



    public static  void  main(String[] args){
        long st = System.currentTimeMillis();
       System.out.println( sum(0));
        System.out.println("sum done : " + (System.currentTimeMillis() - st) + " msecs");
        long st2 = System.currentTimeMillis();
       System.out.println(parallelSum(1080l));
        System.out.println("parallelSum done : " + (System.currentTimeMillis() - st2) + " msecs");

    }
}