Java8 Stream对两个 List 遍历匹配数据的优化处理操作

package com.stream;

  

import java.util.ArrayList;

import java.util.List;

import java.util.stream.Collectors;

  

/**

 *

 * @ClassName: TwoListCopare

 * @Description: 两个List<对象>取交集\并集\差集</>

 **/

public class TwoListCopare {

  public static void main(String[] args) {

    UserDTO userOld1 = new UserDTO("1","aaa",22);

    UserDTO userOld2 = new UserDTO("2","bbb",32);

    UserDTO userOld3 = new UserDTO("3","ccc",11);

    UserDTO userOld4 = new UserDTO("4","ddd",42);

    UserDTO userOld5 = new UserDTO("5","bbb",22);

    UserDTO userOld6 = new UserDTO("6","eee",24);

  

    UserDTO userNew1 = new UserDTO("7","dada",22);   //新增一个

    UserDTO userNew2 = new UserDTO("2","bbb",32);   //不变一个

    UserDTO userNew3 = new UserDTO("3","kaka",33);   //更新一个

    UserDTO userNew4 = new UserDTO("8","dbdb",42);   //新增一个

    UserDTO userNew5 = new UserDTO("5","bbb",100);   //更新一个

    //当然，少了1,4,6

  

    List<UserDTO> mapAdd = new ArrayList<>();

  

    List<UserDTO> oldList = new ArrayList<>();

    List<UserDTO> newList = new ArrayList<>();

  

    //添加老数据

    oldList.add(userOld1);

    oldList.add(userOld2);

    oldList.add(userOld3);

    oldList.add(userOld4);

    oldList.add(userOld5);

    oldList.add(userOld6);

    //添加新数据

    newList.add(userNew1);

    newList.add(userNew2);

    newList.add(userNew3);

    newList.add(userNew4);

    newList.add(userNew5);

  

    //去交集,既获取id相同的交集，需要更新

    //1.先提取出id和结果，用map形式

    List<String> oldIds = new ArrayList<>();

    List<String> newIds = new ArrayList<>();

    oldList.stream().forEach(it->oldIds.add(it.getId()));

    newList.stream().forEach(it->newIds.add(it.getId()));

//    oldIds.stream().forEach(System.out::println);

//    newIds.stream().forEach(System.out::println);

  

    //取交集id

    System.out.println("-----------------交集----------------------");

    List<String> collectUpdate = newIds.stream().filter(it -> oldIds.contains(it)).collect(Collectors.toList());

    collectUpdate.stream().forEach(System.out::println);

    //取对应交集的对象

    System.out.println("------------------交集的对象---------------------");

    List<UserDTO> userUpdate = newList.stream().filter(it -> collectUpdate.contains(it.getId())).collect(Collectors.toList());

    userUpdate.stream().forEach(System.out::println);

  

    //取old的差集

    System.out.println("-----------------old的差集----------------------");

    List<String> collectDelete = oldIds.stream().filter(it -> !newIds.contains(it)).collect(Collectors.toList());

    collectDelete.stream().forEach((System.out::println));

    //取对应old差集对象

    System.out.println("-----------------old差集对象----------------------");

    List<UserDTO> userDelete = oldList.stream().filter(it -> collectDelete.contains(it.getId())).collect(Collectors.toList());

    userDelete.stream().forEach(System.out::println);

  

    //取new的差集

    System.out.println("-----------------new的差集----------------------");

    List<String> collectAdd = newIds.stream().filter(it -> !oldIds.contains(it)).collect(Collectors.toList());

    collectAdd.stream().forEach((System.out::println));

    //取对应old差集对象

    System.out.println("-------------------old差集对象--------------------");

    List<UserDTO> userAdd = newList.stream().filter(it -> collectAdd.contains(it.getId())).collect(Collectors.toList());

    userAdd.stream().forEach(System.out::println);

  

    //取并集

    System.out.println("-------------------并集--------------------");

    List<String> allIds = new ArrayList<>();

    //获取一个包含了oldIds和newIds的总结合,但是没有去重

    allIds.addAll(oldIds);

    allIds.addAll(newIds);

    //去重，获取并集ids的新集合

    List<String> joinIds = allIds.stream().distinct().collect(Collectors.toList());

    joinIds.stream().forEach(System.out::println);

  }

}

package com.shijiayun.api.interfaces.controller.management;


public class UserDTO {


    private String id;

    private String name;

    private Integer age;

    public UserDTO(String id, String name, Integer age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "UserDTO{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}