小编Jos*_*ray的帖子

我在尝试按重量对这些Pet对象进行排序时遇到错误.我确信这很简单,但我不明白为什么这个比较不起作用.

错误:返回类型与java.util.Comparator.compare(Pet,Pet)不兼容

ArrayListNoDups类

import java.util.*;
import java.util.Collections;
import java.util.Comparator;
import java.lang.Object;

public class ArrayListNoDups {
    public static void main(String[] args) {
        ArrayList<Pet> list = new ArrayList<Pet>();
        String name;
        Integer age;
        Double weight;
        Scanner keyboard = new Scanner(System.in);
        System.out.println("If you wish to stop adding Pets to the list, please put a 0 for all 3 fields.");

        do {
            System.out.println("Enter a String for Pet name: ");
            name = keyboard.next();
            System.out.println("Enter an int for Pet age: ");
            age = keyboard.nextInt();
            System.out.println("Enter a double …