Question

我有一个包含不同类型门票的程序。我有Ticket，AdvanceTicket和StudentAdvanceTicket。我打印机票的价格为50美元，预售票价为30美元和40美元），学生预售票的价格分别为15美元和20美元。

条件为if daysAhead >= 10的两个选项。

我花了好几个小时试图解决这个问题，我需要帮助。

Ticket.java

public class Ticket {
  private int number;

  public Ticket(int number) {
    this.number = number;
  }

  public double getPrice() {
    return 50.0;
  }

  public String toString() {
     return "Ticket #" + this.number + ", Price: $" + this.getPrice();
  }
}

TicketMain.java

public class TicketMain {
   public static void main(String[] args) {
      Ticket[] tickets = new Ticket[5];
      tickets[0] = new WalkupTicket(1);
      tickets[1] = new AdvanceTicket(2,12);
      tickets[2] = new AdvanceTicket(3,8);
      tickets[3] = new StudentAdvanceTicket(4,17);
      tickets[4] = new StudentAdvanceTicket(5,7);

      for (int i = 0; i<5; i++) {
         System.out.println(tickets[i]);
         //System.out.println(" ");
      }
   }
}

AdvanceTicket.java

public class AdvanceTicket extends Ticket {
  private int daysAhead;

  public AdvanceTicket(int number, int daysAhead) {
    super(number);
    this.daysAhead = daysAhead;
  }

  public double getPrice() {
    if (daysAhead >= 10) {
      return 30.00;
    } else {
      return 40.00;
    }
  }

  public String toString() {
    if (daysAhead >= 10) {
      return super.toString() + " (" + this.daysAhead + " days ahead, you got a great deal!)";
    } else {
      return super.toString() + " (" + this.daysAhead + " days ahead, you could have saved a bit more)";
    }
  }
}

最后问题...... StudentAdvanceTicket.java

public class StudentAdvanceTicket extends AdvanceTicket {

  public StudentAdvanceTicket(int number, int daysAhead) {
    super(number, daysAhead);
    super.price = super.getPrice() / 2;
  }

  public String toString() {
    return super.toString() + " (ID Required) ";
  }
}

这是我想要的输出。

Ticket #1, Price: $50.0
Ticket #2, Price: $30.0 (12 days ahead, you got a great deal!)
Ticket #3, Price: $40.0 (8 days ahead, you could have saved a bit more)
Ticket #4, Price: $15.0 (ID Required)
Ticket #5, Price: $20.0 (ID Required)

Answer 1

当您致电getPrice() StudentAdvanceTicket时，您的计划实际上会调用AdvanceTicket的实施，这将返回30美元或40美元。

现在当您为toString()致电StudentAdvanceTicket时，它会从toString拨打super，AdvanceTicket就是getPrice()对象的price方法，再次只返回30美元或40美元，并且不会使用getPrice成员变量。

正确的解决方案是覆盖StudentAdvanceTicket类的super.getPrice()。在该方法中，您调用.btn_primary_cancel { a#{&} { line-height: 4rem; } }，然后使用该操作进行价格操作。

Answer 2

在StudentAdvanceTicket中存在编译错误，因为super.price无法解析。

带有继承的Java Ticket程序

2 个答案: