如何在子类中调用超类的参数，以便可以使用变量进行更多计算？

如何解决如何在子类中调用超类的参数，以便可以使用变量进行更多计算？

这是代码，当您对我要完成的事情感到好奇时仅供您参考：

import java.util.EmptyStackException;

public class TicketMain {

    public static void main(String[] args) {
        // Create a Student Ticket
        StudentTicket t1 = new StudentTicket(100,true);
        t1.setPromotionCode("KEXP call-in winner");
        System.out.println(t1);

        // Generate a general ticket
        Ticket t2 = new Ticket(55,40);
        System.out.println(t2);

        // Generate a student ticket
        StudentTicket t3 = new StudentTicket(90,false);
        t3.setPromotionCode("KEXP call-in winner");
        System.out.println(t3);

        // Check for equality
        System.out.println("Ticket t1 and Ticket t2 are equal: " + t1.equals(t2));  // Should return false
        System.out.println("Ticket t1 and Ticket t3 are equal: " + t1.equals(t3));  // Should return true

        // Total tickets generated
        System.out.println("Total Tickets generated so far: " + Ticket.getTicketCount());
    }
}

class Ticket {

    private double price;
    private int daysEarly;
    private String promotionCode;
    private static final String emptyString = "";

    private static int ticketID;                    // Generates ticket number

    public Ticket (double price,int daysEarly) {    // Constructs ticket with given price,# of days early,no promo,assigns ticket #
        this.price = price;
        this.daysEarly = daysEarly;
        ticketID += 1;

        if (ticketID < 0) {
            throw new EmptyStackException();
        }
    }

    public int getDaysEarly(){
        return daysEarly;
    }

    public double getPrice() {
        return price;
    }

    public String getPromotionCode(){
        if (promotionCode == null) return emptyString;
        if (promotionCode.equals("KEXP call-in winner")) promotionCode = ("KEXP call in winner (student)");
        return promotionCode;
    }

    public String setPromotionCode(String code){
        if (code == null) throw new Error();
        this.promotionCode = code;
        return promotionCode;
    }

    public String toString(){
        return "Ticket ID: " + ticketID + ",Price: $" + getPrice() + ",Days Early: " + getDaysEarly() + ",Promotion Code: " + getPromotionCode() + ".";
    }

    public static int getTicketCount(){
        return ticketID;
    }

    public boolean equals(Ticket one) {
        if (price == one.price && promotionCode.equals(one.promotionCode)) return true;
        else return false;
    }

}

以下是我要对超级参数进行数学运算的区域... 我在sub的参数中放入了“ price / 2”来进行数学处理，但是我仍然需要比喻另一个“ if语句”

class StudentTicket extends Ticket {

    private static final int daysEarly = 14;

    public StudentTicket(double price,boolean honors) {
        /*
        Student tickets are always bought by campus ticket sales agency,two weeks in advance.
        Students always get 50% off initial price.
        Honor students get an addition $5 off after the 50%,down to a minimum of $0.
        Student tickets have special promo codes.
         */
        super(price/2,daysEarly);

        // HOW DO I CALL UPON SUPER AFTER ALREADY HAVING DONE SO ???
        // I STILL NEED TO SUBTRACT 5 BASED ON HONORS BOOLEAN OF SUBCLASS
        // HOW DO I ADD AN IF STATEMENT INTO PARAM OF SUPER ???

        // All you will do is make a call to super constructor and pass appropriate parameters
        // So the idea is when I create a instance of StudentTicket and return price it should return me a discounted.
        // That means you need to override the getPrice() method in superclass to update the ticket price

    }

}

有人告诉我重写getPrice方法，但是我不知道有什么方法可以访问子参数

解决方法

您可以在票证类中创建setPrice（）方法：

    ...

    public int getDaysEarly(){
        return daysEarly;
    }

    public void setPrice(double newPrice){
        price = newPrice;
    }
    
    public double getPrice() {
        return price;
    }

    ...

然后在StudentTicket构造函数中执行此操作：

    public StudentTicket(double price,int daysEarly,boolean honors) {
        super(price/2,daysEarly);

        if(honors == true)
            setPrice(getPrice() - 5);
    }

因为您的方法是 public 类型，并且StudentTicket是Ticket类的子类，所以它应该能够访问和利用受任何 public 或保护的来自其父级的方法。

• 或者您可以像wang haoyu所说的那样，声明价格受保护。