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 +
                '}';
    }
}