for循环、并行流、串行流效率比较

User类

import lombok.AllArgsConstructor;import lombok.Builder;import lombok.Data;import lombok.NoArgsConstructor;

@Builder@Data@AllArgsConstructor@NoArgsConstructorpublic class User {    int id;    String name;    int sex;    int age;

}

测试类

import org.springframework.web.bind.annotation.RestController;

import java.time.LocalDateTime;import java.time.temporal.TemporalField;import java.util.ArrayList;import java.util.List;import java.util.stream.Collectors;

@RestControllerpublic class TestController {

    public static void main(String[] args) {        List<User> userList = new ArrayList<>();        for (int i = 0; i < 100; i++) {            int sex = 0;            if ((i & 1) == 1) {                sex = 1;            }            User user = User.builder().id(i).name("刘-" + i).sex(sex).age(i).build();            userList.add(user);        }        System.out.println("=====数据总量：" + userList.size());

        long beginTime = System.currentTimeMillis();        int sumAge1 = 0;        for (User user : userList) {            sumAge1 += user.getAge();        }        long endTime = System.currentTimeMillis();        System.out.println("=====增强for循环所用时间 " + (endTime - beginTime) + " 毫秒" + " ，计算结果" + sumAge1);

        beginTime = System.currentTimeMillis();        int sumAge2 = userList.stream().collect(Collectors.summingInt(User::getAge));        endTime = System.currentTimeMillis();        System.out.println("=====顺序流所用时间 " + (endTime - beginTime) + " 毫秒， 计算结果" + sumAge2);

        beginTime = System.currentTimeMillis();        int sumAge = userList.parallelStream().mapToInt(User::getAge).sum();        endTime = System.currentTimeMillis();        System.out.println("=====并行流所用时间 " + (endTime - beginTime) + " 毫秒， 计算结果" + sumAge);

    }

}

测试结果：

一千五百万的时候并行流最快

到20000000就内存溢出了。

所以通常的处理逻辑for循环性能更优。

原文地址：https://www.cnblogs.com/lalalazar/p/12391393.html