博客

1.TreeSet集合是Set集合中的实现类，底层是二叉树，所以存的数据是不可以重复。可还可以进行排序默认的会对咱们的数据进行排序

2.存储对象时，需要实现Comparabel这个接口。就为了比较排序的

然后在类中重写compareTo(T o)方法

package com.qfedu.b_;

import java.util.Set;
import java.util.TreeSet;

class People implements Comparable <People>{
    private int id;
    private int age;
    private String name;

    public People(int id, int age, String name) {
        this.id = id;
        this.age = age;
        this.name = name;
    }

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

    public int getId() {
        return id;
    }

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

    public int getAge() {
        return age;
    }

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

    public String getName() {
        return name;
    }

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


    @Override
    public int compareTo(People o) {
        /**
         * 此时是按id大小排序，从小到大排
         */
        int num1 = this.id - o.id;

        /**
         * 当id相等时，此时是按照age排的
         */
        if (num1 == 0){
            int num2 = this.age - o.age;
            return num2;
        }
        return num1;
    }
}
public class Demo_24 {
    public static void main(String[] args) {
        /**
         * 实例化TreeSet集合
         */
        Set<People> set = new TreeSet<>();
        /**
         * 实例化几个People对象
         */
        People people1 = new People(1,20,"甘雨");
        People people2 = new People(3,25,"胡桃");
        People people3 = new People(2,18,"雷电将军");
        People people4 = new People(3,30,"枫原万叶");
        People people5 = new People(2,26,"纳西妲");
        /**
         * 把对象存入集合
         */
        set.add(people1);
        set.add(people2);
        set.add(people3);
        set.add(people4);
        set.add(people5);
        System.out.println(set);
        for (People people : set) {
            System.out.println(people);
        }
    }
}