java - Arraylist Java 程序奇怪的输出

Question

首先，我是 ArrayList 的新手。我有一个程序，其中 SalesPerson 对象将前往世界各地的 20 个城市。每次访问时，程序都会要求用户输入城市名称、城市大小和邮政编码。这是使用 for 循环和 ArrayList 完成的。但是当我想显示所有城市时，它打印出奇怪的字符。我可以知道我哪里出错了吗？

Below is the sample output.

Enter name of city: Singapore

Enter size of city: Small

Enter postal code: 132115

==

Enter name of city: Indonesia

Enter size of city: Big

Enter postal code: 111222

==

Cities Visited: [travellingapp.City@42a57993, travellingapp.City@75b84c92]

这是我的代码:

TravellingApp.java

public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        SalesPerson s1 = new SalesPerson();

        for(int j=1; j<=20; j++)
        {
            System.out.print("Enter name of city: ");
            String name = sc.nextLine();

            System.out.print("Enter size of city: ");
            String size = sc.nextLine();

            System.out.print("Enter postal code: ");
            int postalCode = sc.nextInt();
            sc.nextLine();

            System.out.println("___________________________________________");



            City c1 = new City(name, size, postalCode);
            s1.addCity(c1);

        }
        System.out.print("Cities Visited: "+ s1.returnListOfCities());

    }

SalesPerson.java(类)

public class SalesPerson {

    private ArrayList<City>listOfCities = new ArrayList<City>();

    public void addCity(City c1)
    {
        listOfCities.add(c1);
    }

    public ArrayList<City> returnListOfCities()
    {
        return listOfCities;
    }
}

City.java(类)

public class City {

    private String nameOfCity;
    private String sizeOfCity;
    private int postalCode;

    public City(String nameOfCity, String sizeOfCity, int postalCode)
    {
        this.nameOfCity = nameOfCity;
        this.sizeOfCity = sizeOfCity;
        this.postalCode = postalCode;
    }

    public String getNameOfCity() {
        return nameOfCity;
    }

    public String getSizeOfCity() {
        return sizeOfCity;
    }

    public int getPostalCode() {
        return postalCode;
    }

    public void setNameOfCity(String nameOfCity) {
        this.nameOfCity = nameOfCity;
    }

    public void setSizeOfCity(String sizeOfCity) {
        this.sizeOfCity = sizeOfCity;
    }

    public void setPostalCode(int postalCode) {
        this.postalCode = postalCode;
    }   


}

Answer 1

当您调用 s1.returnListOfCities() 时，该方法会返回 City 对象的数组列表。 System.out.println() 无法识别此格式。

您可以使用迭代器来迭代Arraylist。

    Iterator<City> iterator = s1.returnListOfCities().iterator();
    while(iterator.hasNext()){
      System.out.println(iterator.next().getNameOfCity());
    }