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 +
                '}';
    }
}

 

 

标签：Stream,stream,List,System,new,UserDTO,Java8,out
来源： https://www.cnblogs.com/xzcBY/p/14047155.html