Java之Set 交集,差集,并集的用法_开发_开发者

Java之Set 交集,差集,并集

/**
 * Created by yuhui on 2017/7/11 0011.
 */
import java.util.HashSet;
import java.util.Set;
public class TestSet {
    public static void main(String[] args) {
        Set<String> result = new HashSet<String>();
        Set<String> set1 = new HashSet<String>() {
            {
                add("王者荣耀");
                add("英雄联盟");
                add("穿越火线");
                add("地下城与勇士");
            }   
        };
        Set<String> set2 = new HashSet<String>() {
            {
                add("王者荣耀");
                add("地下城与勇士");
                add("魔兽世界");
            }
        };
        result.clear();
        result.addAll(set1);
        result.retainAll(set2);
        System.out.println("交集：" + result);
        result.clear();
        result.addAll(set1);
        result.removeAll(set2);
        System.out.println("差集：" + result);
        result.clear();
        result.addAll(set1);
        result.addAll(set2);
        System.out.println("并集：" + result);
    }js
}

结果如下：

交集：[王者荣耀, 地下城与勇士]
差集：[英雄联盟, 穿越火线]
并集：[王者荣耀, 英雄联盟, 魔兽世界, 地下城与勇士, 穿越火线]

java8 list<bean>交集差集并集

定义bean

public class Student {
  private String Id ;
  private String name;
  private String age;
  public void setAge(String age) {
    this.age = age;
  }
  public String getAge() {
    return age;
  }
  public String getId() {
    return Id;
  }
  public String getName() {
    return name;
  }
  public void setId(String id) {
    Id = id;
  }
  public void setName(String name) {
    this.name = name;
  }
}

定义两个list

list 1

List<Student> list1 = new ArrayList<Student>();
Student st1 = new Student();
st1.setId("2");
st1.setName("");
st1.setAge("");
list1.add(st1);
Student sta = new Student();
sta.setId("1");
sta.setName("");
sta.setAge("");
list1.add(sta);

list 2

List<Student> list2 = new ArrayList<Student>();
Student st2 = new Student();
st2.setId("2");
st2.setName("");
st1.setAge("");
list2.add(st2);

找出id存在list1不存在list2的数据——差集 (list1 - list2)
// 差集 (list1 - list2)
Li开发者_JAV培训st<Student> distinctByUniqueList = list1.stream()
                  .filter(item -> !list2.stream()
                   .map(e -> e.getId() )
                   .collect(Collectors.toList())
                .contains(item.getId()))
                .collect(Collectors.toList());

结果：
System.out.println("---差集 reduce1 (list1 - list2)---");
for(Student st : distinctByUniqueList){
System.out.println(st.getId());
System.out.println(st.getName());
}

---差集 reduce1 (list1 - list2)---
1

找出id存在list1同时存在list2的数据——交集

List<Student> intersection = list1.stream()
           .filter(item -> list2.stream()
                  .map(e -> e.getId())
                 .collect(Collectors.toList())
                 .contains(item.getId()))
              .collect(Collectors.toList());

结果：
System.out.println("---交集 intersection---");
for(Student st : intersection){
System.out.println(st.getId());
System.out.println(st.getName());
}

---交集 intersection---
2

获取distinctByUniqueList 与intersection并集

List<Student> add1 = istinctByUniqueList.parallelStream().collect(toList());
List<Student> add2 = intersection.parallelStream().collect(toList());
add1.addAll(add2);

结果：

结果：
System.out.println("---并集 listAll---");
for(Student st : add1){
System.out.println(st.getId());
System.out.println(st.getNam编程e());
编程客栈;}

---并集 listAll---
2

1http://www.devze.com

源码

import java.util.ArrayList;
import java.util.List;
import java.util.stream.*;
import static java.util.stream.Collectors.toList;
public class test {
  public static void main(String[] args) {
    List<Student> list1 = new ArrayList<Student>();
    Student st1 = new Student();
    st1.setId("2");
    st1.setName("");
    st1.setAge("");
    list1.add(st1);
    Student sta = new Student();
    sta.setId("1");
    sta.setName("");
    sta.setAge("");
    list1.add(sta);
    List<Student> list2 = new ArrayList<Student>();
    Student st2 = new Student();
    st2.setId("3");
    st2.setName("");
    st1.setAge("");
    list2.add(st2);
    // 差集 (list1 - list2)
    List<Student> distinctByUniqueList = list1.stream()
                      .filter(item -> !list2.stream()
                    .map(e -&iVhHcgt; e.getId() )
                       .collect(Collectors.toList())
                .contains(item.getId()))
                      .collect(Collectors.toList());
    System.out.println("---差集 reduce1 (list1 - list2)---");
    for(Student st : distinctByUniqueList){
      System.out.println(st.getId());
      System.out.println(st.getName());
    }
    // 交集
    List<Student> intersection = list1.stream()
                  .filter(item -> list2.stream()
                      .map(e -> e.getId())
                      .collect(Collectors.toList())
                      .contains(item.getId()))
                  .collect(Collectors.toList());
    System.out.println("---交集 intersection---");
    for(Student st : intersection){
      System.out.println(st.getId());
      System.out.println(st.getName());
    }
    List<Student> add1 = distinctByUniqueList.parallelStream().collect(toList());
    List<Student> add2 = intersection.parallelStream().collect(toList());
    add1.addAll(add2);
    System.out.println("---并集 listAll---");
    for(Student st : add1){
      System.out.println(st.getId());
      System.out.println(st.getName());
    }
  }
}