调用不同类的方法|Java

Question

我正在为一个应用程序编写代码，该应用程序可以跟踪学生在校园自助餐厅购买的食物。有两个类-Student，它包含重载构造函数&适当的吸气剂&setter方法；和MealCard，它包含一个类变量来跟踪发放的餐卡数量，适当的getter&setter方法、purchaseItem（）方法、purhasePoints（）方法&被重写的toString（）方法。还有一个测试程序类。

在我的MealCard类中，方法是编写的，但在Tester中，当我调用它们时，它们无法正常工作。我想从用户那里获得itemValue，但如何在MealCard类中做到这一点？

purchasePoints方法也是如此，我如何从MealCard类中的用户那里获得topUpValue？

到目前为止的代码是：

public class Student {
// Instance Variables
private String name;
private int age;
private String address;
// Default Constructor
public Student() {
    this("Not Given", 0, "Not Given");
}
// Parameterized constructor that takes in values
public Student(String name, int age, String address) {
    this.name = name;
    this.age = age;
    this.address = address;
}
// Getters and Setters
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public int getAge() {
    return age;
}
public void setAge(int age) {
    this.age = age;
}
public String getAddress(){
    return address;
}
public void setAddress(String address) {
    this.address = address;
}
// toString() to be overriden
@Override
public String toString() {
    return "Name: " + this.name + "n" + "Age: " + this.age + "n" + "Address: " + this.address;
}
}

`

public class MealCard extends Student {
static int numberOfMealCards;
private final static int DEFAULT_BALANCE = 1000;
private int itemValue;
private int topUpValue;
public int newBalance;
// Getters and Setters
public int getItemValue() {
    return itemValue;
}
public void setItemValue(int itemValue) {
    this.itemValue = itemValue;
}
public int getTopUpValue() {
    return topUpValue;
}
public void setTopUpValue(int topUpValue) {
    this.topUpValue = topUpValue;
}
// purchaseItem method for when students buy food
public int purchaseItem() {
    newBalance = DEFAULT_BALANCE - itemValue;
    return newBalance;
}
// purchasePoints method for students topping up their meal card balance
public int purchasePoints() {
    newBalance = DEFAULT_BALANCE + topUpValue;
    return newBalance;
}
// Overriden toString method
@Override
public String toString() {
    return super.toString() + "Meal Card Balance: " + this.newBalance + "n" + "Number of Meal Cards: " + numberOfMealCards;
}
}

`

import java.util.Scanner;
public class TestMealCard {
public static void main(String[] args) {
    // Create instances of MealCard class
    MealCard student1 = new MealCard();
    MealCard student2 = new MealCard();
    Scanner keyboard = new Scanner(System.in);
    System.out.println("Name: ");
    student1.setName(keyboard.nextLine()); 
    System.out.println("Age: ");
    student1.setAge(keyboard.nextInt()); 
    System.out.println("Address: ");
    student1.setAddress(keyboard.nextLine()); 
    System.out.println("Meal Card Balace: ");
    student1.newBalance = keyboard.nextInt();
    System.out.println("Number of Meal Cards Issued: ");
    student1.numberOfMealCards = keyboard.nextInt();
    System.out.println("Name: ");
    student2.setName(keyboard.nextLine()); 
    System.out.println("Age: ");
    student2.setAge(keyboard.nextInt()); 
    System.out.println("Address: ");
    student2.setAddress(keyboard.nextLine()); 
    System.out.println("Meal Card Balace: ");
    student2.newBalance = keyboard.nextInt();
    System.out.println("Number of Meal Cards Issued: ");
    student2.numberOfMealCards = keyboard.nextInt();
    // Call purchaseItem
    student1.purchaseItem();

    // Call purchasePoints
    student2.purchasePoints();
    // Call tString to output information to user
}
}

Answer 1

为了从用户处设置itemValue，您需要使用此setItemValue（）方法从用户处获取输入。

Ex。

System.out.print("Please enter the item value:   ");
student1.setItemValue(keyboard.nextInt());

或

int itemVal = 0;
System.out.print("Please enter the item value:   ");
itemVal = keyboard.nextInt();
student1.setItemValue(itemVal);

至于另一个方法调用，只需调用toUpValue的setter。

Ex。

System.out.print("Please enter the item value:   ");
student1.setTopUpValue(keyboard.nextInt());

或

int toUpVal = 0;
System.out.print("Please enter the item value:   ");
itemVal = keyboard.nextInt();
student1.setTopUpValue(topUpVal);

希望有帮助。