不确定如何使用 Java Scanner 创建对象并将其存储在 ArrayList 中

Question

我目前正在尝试使用 Java Scanner 输入创建一个对象。

此对象CashCard 包含字段amount、name 和amountcardisused。

但我不确定如何从 java Scanner 获取输入并将其移动到我的 ArrayList CashCard 中。

到目前为止，这是我的代码，我不知道如何继续，希望你能帮助我。

班级Cashcard

package cashcard;

import java.util.ArrayList;

public class CashCard {

    private double amount;
    private String name;
    private int amountcardisused;
    private ArrayList<CashCard> listofcashcards;

    public CashCard(String name, double amount, int amountcardisused){
        this.amount = amount;
        this.name = name;
        this.amountcardisused = amountcardisused;
        listofcashcards = new ArrayList<CashCard>();
}

    public String setName(String name){
        return name;
    }
    public double setAmount(double amount){
        return amount;
    }
    public int setTimesCardIsUsed(int amountcardisused){
        return amountcardisused;
    }
}

班级TestCashCard

package cashcard;

import java.util.*;

public class TestCashCard {

    ArrayList<CashCard> listofcashcards = new ArrayList<CashCard>();

    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);
        String input;

        // Stop console when entering 0 in console
        System.out.println("0: Stop Program");
        System.out.println("1: Add CashCard");

        // Execute this code when entering 1 in console
        System.out.println();
        System.out.print("Enter 0 or 1: ");
        input = in.nextLine();

        if(input.equals("0")){
        System.exit(0);
        }

        else if(input.equals("1")){

        System.out.print("Enter name of the card owner: ");
        String yourname = in.nextLine();

        System.out.println("Enter the amount you want to set on your cashcard: ");
        double youramount = in.nextDouble();

        System.out.print("Enter The Amount This Card Is Already Used: ");
        int youramountcardisused = in.nextInt();

        // Do Something to create an CashCard object by using the scanner its input 
        // and than put the object inside the ArrayList CashCard.
        // Need help on this part

    }

    else{
        System.out.print("No choice is made, close program");
        System.exit(0);
    }
  }
}

Answer 1

您的CashCard 不应包含ArrayList 的CashCard 对象。您可以删除它并将您的 ArrayList 保留在您的主课程中。

所以你可以在你的 main 中这样做：

ArrayList<CashCard> myCashCards = new ArrayList<CashCard>();

//Scanner input here.

CashCard cashCard = new CashCard(yourname, youramount, youramountcardisused);

myCashCards.add(cashCard);

Answer 2

你唯一需要做的就是

public CashCard(String name, double amount, int amountcardisused){
    this.amount = amount;
    this.name = name;
    this.amountcardisused = amountcardisused;
    //remove the below line from here
    listofcashcards = new ArrayList<CashCard>();// dont include this here
  }

在你的 testcashcard 类中

之后

  System.out.print("Enter The Amount This Card Is Already Used: ");
        int youramountcardisused = in.nextInt();

添加

CashCard cashcard1 = new CashCard("abc",1000,2);

listofcashcards.add(cashcard1);

Answer 3

如果您希望在 CashCard 类（而不是测试类）中保留所有已创建 CashCard 的列表，请将 ArrayList 字段设为静态，如下所示：

private double amount;
private String name;
private int amountcardisused;
// change your line below to this
private static ArrayList<CashCard> listofcashcards = new ArrayList<CashCard>();

为您的 ArrayList 字段编写两个访问方法（同样在您的 CashCard 类中）：

public static void addCashCard(CashCard cc) {
    listofcashcards.add(cc);
}

public static ArrayList<CashCard> getAllCashCards() {
    // Return new list copied from field (for field protection)
    return new ArrayList<CashCard>(listofcashcards);
}

然后，当您想使用测试类添加新卡时，请使用构造函数和 addCashCard 方法将新卡存储在共享字段中：

...

System.out.print("Enter The Amount This Card Is Already Used: ");
int youramountcardisused = in.nextInt();

// Create your object using the constructor, and add it to your list,
// which lives inside your CashCard class
CashCard.addCashCard(new CashCard(yourname, youramount, youramountcardisused));

...

瞧！如果你想从你的测试类中访问你所有的卡片，只需调用 CashCard.getAllCashCards()