将新对象追加到数组列表的开头[重复]

Question

问题是：“要求用户输入其国家的详细信息，使用输入的值创建一个国家的新对象，并将其附加到数组列表的开头。”

我确实遵循了最基本的规则来防止任何错误，但是当我试图编译时。它复制了一些像日本和美国这样的物体。尝试许多不同的方法来调试和理解问题，但我找不到。

import java.util.*;

public class Country{
    private String name;
    private String continent;
    private int area;
    private double population;

    //Constructor, mutator, accessor method minimized    

    public String toString() {
        return "Name: " + name + ", Continent: " + continent + ", Area: " + area + ", Population: " + population;
    }


    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        ArrayList<Country> ct = new ArrayList<>();

        ct.add(new Country("Nepal", "Asia", 147516, 29.14));
        ct.add(new Country("Japan", "Asia", 377975, 125.8));
        ct.add(new Country("Kazakhstan", "Asia", 2725000, 18.75));
        ct.add(new Country("United States", "North America", 9834000, 329.5));
        ct.add(new Country("Australia", "Oceania", 7692000, 25.69));

        System.out.print("Your country name:");
        String name = sc.nextLine();
        System.out.print("Continent: ");
        String continent = sc.nextLine();
        System.out.print("Area: ");
        int area = sc.nextInt();
        System.out.print("Population: ");
        double population = sc.nextDouble();
        ct.add(0, new Country(name, continent, area, population));

        for(Country country : ct){
        System.out.println(country.toString());
            if(country.getContinent().contains("Asia")){
                System.out.println(country.toString());
            }
            if(country.getPopulation() >= 100 && country.getPopulation() <= 500){
                System.out.println(country);
            }
        }
    }
}

Answer 1

您可能需要的是：

ct.add(0, new Country("Nepal", "Asia", 147516, 29.14));
ct.add(0, new Country("Japan", "Asia", 377975, 125.8));