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
@NoArgsConstructor
public 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;

@RestController
public 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。