Question

import java.util.*;
public class testPerson{
    public static void main(String[] args){
        person Albert = new person(1);
        person James = new person(2);
        person Elizabeth = new person(3);
        person [] personArray = new person[3];
        personArray[0] = Albert;
        personArray[1] = James;
        personArray[2] = Elizabeth;
        Arrays.sort(personArray);
        System.out.println(personArray[0].number);
        System.out.println(personArray[1].number);
        System.out.println(personArray[2].number);
    }
}

public class person implements Comparable{
    int number;
    public person(int number){
        this.number = number;
    }
    public int compareTo(Object o){
        if(!(o instanceof person)){
            System.out.println("error");
            System.exit(1);
            person newObject = (person) o;
            if (this.number > newObject.number){
                return 1;
            }
            else if(this.number == newObject.number){
                return 0;
            }
        }
        return -1;
    }
}

我很困惑为什么输出会向后排序：3,2,1。当this.number＆gt;数字时，我的compareTo方法返回一个正数，所以不应该确保数字按顺序排序 - 从最小到最大？感谢

Answer 1

compareTo方法中的错误总是返回-1。不过，您可以通过实施compareTo而不是Comparable<Person>来简化Comparable方法：

class Person implements Comparable<Person> {
    public int compareTo(Person other) {
        return this.number - other.number;
    }
}

Answer 2

您只需要将compareTo方法更改为以下内容，因此如果传递的不是person的实例，它可以返回错误，否则它将转换传递的对象并进行比较：

 public int compareTo(Object o){
    if(!(o instanceof person)){
        System.out.println("error");
        System.exit(1);
    }

    person newObject = (person) o;
    if (this.number > newObject.number){
       return 1;
    }
    else if(this.number == newObject.number){
       return 0;
    }
    return -1;
}

可比的Java排序

2 个答案: