treemap

treeMap

类需要实现comparable
需要重写compareTo

import java.util.TreeMap;

public class Demo01 {
    public static void main(String[] args) {

        //创建集合
        TreeMap<Student, String> treeMap = new TreeMap<>();
        //1添加元素
       Student s1 = new Student("孙悟空", 01);
       Student s2 = new Student("猪八戒", 02);
       Student s3 = new Student("沙和尚", 03);

        treeMap.put(s1, "北京");
        treeMap.put(s2, "上海");
        treeMap.put(s3, "北京");
        System.out.println(treeMap);
    }
}

package Collection.Map.Demo03;


import java.util.Objects;

public class Student implements Comparable <Student>{
    private String name;
    private int stuNo;

    public Student() {
    }

    public Student(String name, int stuNo) {
        this.name = name;
        this.stuNo = stuNo;
    }

    public String getName() {
        return name;
    }

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

    public int getStuNo() {
        return stuNo;
    }

    public void setStuNo(int stuNo) {
        this.stuNo = stuNo;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", stuNo=" + stuNo +
                '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Student)) return false;
        Student student = (Student) o;
        return getStuNo() == student.getStuNo() && Objects.equals(getName(), student.getName());
    }

    @Override
    public int hashCode() {
        return Objects.hash(getName(), getStuNo());
    }

    @Override
    public int compareTo(Student o) {
        //int n1 = this.name.compareTo(o.getName());
        int n2 = this.stuNo-o.stuNo;
        return n2;
    }
}