TreeSet实现自定义排序

public class User implements Comparable{
    private String name;
    private int age;

    public User() {
    }

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

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

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

    @Override
    public boolean equals(Object o) {
        System.out.println("User equals()....");
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        User user = (User) o;

        if (age != user.age) return false;
        return name != null ? name.equals(user.name) : user.name == null;
    }

    @Override
    public int hashCode() { //return name.hashCode() + age;
        int result = name != null ? name.hashCode() : 0;
        result = 31 * result + age;
        return result;
    }

    //按照姓名从大到小排列,年龄从小到大排列
    @Override
    public int compareTo(Object o) {
        if(o instanceof User){
            User user = (User)o;
//            return -this.name.compareTo(user.name);
            int compare = -this.name.compareTo(user.name);
            if(compare != 0){
                return compare;
            }else{
                return Integer.compare(this.age,user.age);
            }
        }else{
            throw new RuntimeException("输入的类型不匹配");
        }

    }
}

 方式二：

   @Test
    public void test2(){
        Comparator com = new Comparator() {
            //按照年龄从小到大排列
            @Override
            public int compare(Object o1, Object o2) {
                if(o1 instanceof User && o2 instanceof User){
                    User u1 = (User)o1;
                    User u2 = (User)o2;
                    return Integer.compare(u1.getAge(),u2.getAge());
                }else{
                    throw new RuntimeException("输入的数据类型不匹配");
                }
            }
        };

        TreeSet set = new TreeSet(com);
        set.add(new User("Tom",12));
        set.add(new User("Jerry",32));
        set.add(new User("Jim",2));
        set.add(new User("Mike",65));
        set.add(new User("Mary",33));
        set.add(new User("Jack",33));
        set.add(new User("Jack",56));


        Iterator iterator = set.iterator();
        while(iterator.hasNext()){
            System.out.println(iterator.next());
        }
    }

 

package com.collection;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;

/**
 * @version v1.0
 * @ProjectName: cshjavatest
 * @ClassName: demo01
 * @Description: TODO(一句话描述该类的功能)
 * @Author: CSH
 * @Date: 2020/5/31 9:12
 */
public class Demo01 {
    public static void main(String[] args) {
        Comparator comparator=new Comparator() {
            @Override
            public int compare(Object o1, Object o2) {
                if(o1 instanceof Integer && o2 instanceof Integer){
                    Integer int1=(Integer) o1;
                    Integer int2=(Integer) o2;
//                    方式一
//                    return -Integer.compare(int1,int2);
//                    方式二
                    if (int1>int2){
                        return -1;
                    }else if(int1<int2){
                        return 1;
                    }else {
                        return 0;
                    }
                }else {
                    throw new RuntimeException("输入的数据类型不匹配");
                }
            }
        };
        ArrayList arrayList=new ArrayList();
        arrayList.add(1);
        arrayList.add(95);
        arrayList.add(10);
        arrayList.add(88);
        arrayList.add(-8);
        Collections.sort(arrayList,comparator);
        System.out.println(arrayList);
    }

}