一 需求

以 name phone address 三个字段为关键字，分组计算 scope 的和。

二 代码

package com.cakin.javademo;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;

/**
 * @ClassName: GroupSum
 * @Description: 多字段分组，单字段求和 https://blog.csdn.net/xp_lx1/article/details/109624697
 * @Date: 2021/3/13
 * @Author: cakin
 */
public class GroupSum {
    /**
     * 功能描述：多字段分组，单字段求和 测试
     *
     * @author cakin
     * @date 2021/3/14
     * @param args 命令行
     */
    public static void main(String[] args) {
        List<User> users = new ArrayList<>();
        users.add(new User("tom", "15687675434", "北京", 100l));
        users.add(new User("tom", "15687675434", "北京", 50l));
        users.add(new User("tom", "13654345654", "上海", 77l));
        users.add(new User("jerry", "15976543454", "苏州", 30l));
        users.add(new User("jerry", "15976543454", "苏州", 40l));
        List<User> userList = new ArrayList<>();
        // 以 name phone address 三个字段为关键字，分组计算 scope 的和。
        users.stream().collect(Collectors
                .groupingBy(user -> new User(user.getName(), user.getPhone(), user.getAddress()), Collectors.summarizingLong(user -> user.getScope())))
                .forEach((k, v) -> {
                    k.setScope(v.getSum());
                    userList.add(k);
                });
        for (User user : userList) {
            System.out.println(user);
        }
    }
}

/**
 * @ClassName: User
 * @Description: 用户类
 * @Date: 2021/3/13
 * @Author: cakin
 */
class User {
    public String name;
    public String phone;
    public String address;
    public Long scope;

    public User(String name, String phone, String address) {
        this.name = name;
        this.phone = phone;
        this.address = address;
    }

    public User(String name, String phone, String address, Long scope) {
        this.name = name;
        this.phone = phone;
        this.address = address;
        this.scope = scope;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public Long getScope() {
        return scope;
    }

    public void setScope(Long scope) {
        this.scope = scope;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", phone='" + phone + '\'' +
                ", address='" + address + '\'' +
                ", scope=" + scope +
                '}';
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, phone, address);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        User user = (User) o;
        return Objects.equals(name, user.name) &&
                Objects.equals(phone, user.phone) &&
                Objects.equals(address, user.address) &&
                Objects.equals(scope, user.scope);
    }
}

三 测试

User{name='tom', phone='15687675434', address='北京', scope=150}
User{name='jerry', phone='15976543454', address='苏州', scope=70}
User{name='tom', phone='13654345654', address='上海', scope=77}

标签：Java,name,单字,public,phone,User,address,scope,多字段
来源： https://blog.csdn.net/chengqiuming/article/details/114776747