Java基础- TreeMap<Person,Integer> 实现的定制排序(Comparator 接口)

测试内容:

TreeMap<Person,Integer> 的两级排序
1.先按Person.id 从小到大   (需要把int类型转换成包装类 Integer, 才可以使用p1.getId().compareTo( p2.getId()))
2.若id重复,则按然后再按Person.Name 从小到大排序(可以使用String类内置的 compareTo())

测试代码:

package 任务151;
import java.lang.*;
import java.util.*;
public class TestTreeMap {

    public static void main(String[] args) {
        Comparator comp=new Comparator() {
            @Override
            public int compare(Object o1, Object o2) {
                if(o1 instanceof Person && o2 instanceof Person) {
                    Person p1 = (Person) o1;
                    Person p2 = (Person) o2;                      //先按Person.id 从小到大
                    if (p1.getId().compareTo( p2.getId()) ==0 )   //然后再按Name 从小到大排序
                        return p1.getName().compareTo(p2.getName());
                    else
                        return p1.getId().compareTo( p2.getId());
                }
                return 0; 
            }
        };
        Map<Person,Integer> mp=new TreeMap<>(comp);
        mp.put(new Person("AA",22),788);
        mp.put(new Person("BB",24),783);
        mp.put(new Person("GG",42),718);
        mp.put(new Person("DD",42),178);
        Set st1=mp.keySet();
        for(Object o:st1){
            Person p=(Person)o;
            System.out.println("["+p.name+","+p.id+"]"+": "+mp.get(o));   //构成键--值对
        }
    }

}
class Person{
    String name;
    Integer id;
    public Person(String name, int id) {
        this.name = name;
        this.id = (Integer)id;
    }

    public String getName() {
        return name;
    }

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

    public Integer getId() {
        return id;
    }

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

结果:

[AA,22]: 788
[BB,24]: 783
[DD,42]: 178
[GG,42]: 718