TreeSet集合

package com.day0307_1;
import org.junit.jupiter.api.Test;
import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeSet;
/**
 *
 */
public class TreeSetTest {
    /*
    1.向TreeSet中添加的数据，要求是相同类的对象。
    2.两种排序方式：自然排序（实现Comparable接口）和定制排序（comparator）
    3.自然排序中，比较两个对象是否相同的标准为：compareTo()返回0，不在是equals()。
    4.定制排序中，比较两个对象是否相同的标准为：compare()返回0，不再是equals()。
     */
    @Test
    public void test1(){
        TreeSet set=new TreeSet();
        //失败：不能添加不同类的对象
//        set.add(123);
//        set.add(456);
//        set.add("AA");
//        set.add(new User("Tom",12));
        //举例一：
//        set.add(34);
//        set.add(-34);
//        set.add(43);
//        set.add(11);
//        set.add(8);
        //举例二：
        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("Jack",33));
        set.add(new User("Jack",56));
        Iterator iterator= set.iterator();
        while (iterator.hasNext()){
            System.out.println(iterator.next());
        }
    }
    @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.day0307_1;
import java.util.Objects;
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;
        return age == user.age &&
                Objects.equals(name, user.name);
    }
    @Override
    public int hashCode() {
        return Objects.hash(name, age);
    }
    //按姓名从大到小,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");
        }
    }
}