簡介

Comparable<> 介面

Compatator 也是介面 -- 類似C++中的cmp函式.

分別對一個物件實現了 從大到小排序和從小到大排序

code

import java.util.*;

/**
 * Created by lee on 2021/6/28.
 */
public class Compara {
    public static void main(String[] args) {
        List<Person1> v = new ArrayList<>();
        for(int i=0; i<100; i++) {
            Person1 p= new Person1(i);
            v.add(p);
        }
        Collections.sort(v);

        for(int i=0; i<10; i++){
            System.out.println(v.get(i));
        }

        System.out.println("=========================================");

        Collections.sort(v, new Comparator<Person1>() {
            @Override
            public int compare(Person1 o1, Person1 o2) {
                return o2.age - o1.age;
            }
        });

        for(int i=0; i<10; i++){
            System.out.println(v.get(i));
        }

    }

}

class Person1 implements Comparable<Person1> {
    public int age;

    public Person1(int a){
        age = a;
    }

    @Override
    public int compareTo(Person1 o) {
        return this.age - o.age ;
    }

    @Override
    public String toString() {
        return ""+age;
    }
}