Java Stream 流进行根据元素某一属性过滤计算其他属性实例

设计一个测试类Tuser

package org.example;

import com.alibaba.fastjson.annotation.JSONField;

import java.io.Serializable;

public class Tuser implements Serializable {

    //用户名
    private String name;
    //平台名称
    private String sys;
    //登录次数
    private int times;
    //一个合并属性的key
    @JSONField(serialize =false)
    private String key;

    public String getKey(){

        return name+sys;
    }

    public String getName() {
        return name;
    }

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

    public String getSys() {
        return sys;
    }

    public void setSys(String sys) {
        this.sys = sys;
    }

    public int getTimes() {
        return times;
    }

    public void setTimes(int times) {
        this.times = times;
    }
}

编写Main测试类

package org.example;

import com.alibaba.fastjson.JSONObject;

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

public class StreamTest {


    public static void main(String[] args) {
        Tuser t1 = new Tuser();
        t1.setName("tom");
        t1.setSys("web");
        t1.setTimes(5);

        Tuser t2 = new Tuser();
        t2.setName("jack");
        t2.setSys("web");
        t2.setTimes(10);

        Tuser t3 = new Tuser();
        t3.setName("lili");
        t3.setSys("app");
        t3.setTimes(12);


        Tuser t4 = new Tuser();
        t4.setName("lili");
        t4.setSys("app");
        t4.setTimes(9);

        Tuser t5 = new Tuser();
        t5.setName("tom");
        t5.setSys("web");
        t5.setTimes(10);


        List<Tuser> tuserList = new ArrayList<>();

        tuserList.add(t1);
        tuserList.add(t2);
        tuserList.add(t3);
        tuserList.add(t4);
        tuserList.add(t5);

        //取出名字并去重
        List<String> userNames = tuserList.stream().map(tuser -> tuser.getName()).distinct().collect(Collectors.toList());
        System.out.println(JSONObject.toJSONString(userNames));

        //找出登陆次数大于5次的数据
        List<Tuser> users = tuserList.stream().filter(tuser -> tuser.getTimes() > 5
        ).collect(Collectors.toList());

        System.out.println(JSONObject.toJSONString(users));

        //找出同一个人登录统一平台的总次数输出新列表
        List<Tuser> tusers = tuserList.stream()
                
                .collect(Collectors.toMap(Tuser::getKey, a -> a, (o1, o2) -> {
                    o1.setTimes(o1.getTimes() + o2.getTimes());
                    return o1;
                })).values().stream().collect(Collectors.toList());


        System.out.println(JSONObject.toJSONString(tusers));
    }


}

输出结果：

//取出名字并去重

["tom","jack","lili"]

//找出登陆次数大于5次的数据

[{"name":"jack","sys":"web","times":10},{"name":"lili","sys":"app","times":12},{"name":"lili","sys":"app","times":9},{"name":"tom","sys":"web","times":10}]

//找出同一个人登录统一平台的总次数输出新列表
[{"name":"tom","sys":"web","times":15},{"name":"jack","sys":"web","times":10},{"name":"lili","sys":"app","times":21}]