Question

所以我正在建立一个使用继承和多态来销售三张票的售票亭。输出需要看起来像这样。

常规季节：

Ticket type: Walkup, Number: 123, Price: 10.00
Ticket type: Advance, Number: 234, Price: 7.50
Ticket type: Student Advance, Number: 345, Price: 3.75 (ID Required)

决赛：

Ticket type: Walkup, Number: 321, Price: 12.00
Ticket type: Advance, Number: 432, Price: 9.00
Ticket type: Student Advance, Number: 543, Price: 4.50 (ID Required)

我的输出就是这个。

常规季节：

Ticket type:  Walkup,  Number:  123,  Price:  10.00
Ticket type:  Advance,  Number:  234,  Price:  10.00
Ticket type:  Student Advance,  Number:  345,  Price:  10.00

决赛：

Ticket type:  Walkup,  Number:  321,  Price:  12.00
Ticket type:  Advance,  Number:  432,  Price:  12.00
Ticket type:  Student Advance,  Number:  543,  Price:  12.00

所以我的问题是如何更改我的代码中的静态双倍价格，使其成为那些价格而不会将整个价格更改为我设置的价格。

继承我的代码：

public abstract class Ticket {

    protected String ticketNumber;
    protected static double price = 10.00;
    protected String ticketName;

    // constructor so i can change my ticket number in the main as a parameter
    public Ticket(String string)  {
        this.ticketNumber = string;
    }

    // get name in other classes
    public String getName()  {
        return ticketName;
    }

    // get price
    public double getPrice()  {
        return price;
    }

    // so i can chang the price in the main 
    public static void setPrice(double price) {
        Ticket.price = price;
    }

    // toString method so i can print my descriptive information.
    public String toString()  {
        String result = String.format("\tTicket type:  %s,  Number:  %s,  Price:  %.2f", getName(), ticketNumber, getPrice());
        return result;
    }
}

public class WalkUpTicket extends Ticket {

    public WalkUpTicket(String string) {
        super(string);

    }

    public String getName()  {
        return this.ticketName = "Walkup";
    }

}

public class AdvanceTicket extends Ticket {

    public AdvanceTicket(String string) {
        super(string);
    }
    public String getName()  {
        return "Advance";   
    }   
}
public class StudentAdvanceTicket extends AdvanceTicket {

    public StudentAdvanceTicket(String string) {
        super(string);

    }

    public String getName()  {
        return "Student Advance";
    }

}

Answer 1

静态实例变量在同一个类的每个实例之间共享。它们类绑定，而不是实例绑定。

如上所述，您需要从Ticket类中删除静态价格，而是将其放在扩展它的每个类中。由于变量是类绑定的，因此每个子类都需要一个。您还必须在每个子类中创建setPrice()方法，以修改每种类型的价格。

Answer 2

此设计模式的最佳折衷方案如下所示Inherit a Static Variable in Java ..如何从静态成员继承静态成员，从顶部答案：

abstract class Parent {
public abstract String getACONSTANT();
}

class Child extends Parent {
    public static final String ACONSTANT = "some value";
    public String getACONSTANT() { return ACONSTANT; }
}

在其他类中更改静态double

2 个答案: