具有继承性的 Java Ticket 程序

Question

我有一个包含不同类型门票的节目。我有 Ticket、AdvanceTicket 和一张 StudentAdvanceTicket。我打印的票价是 50 美元，预售票的价格是 30 美元和 40 美元)，学生预售票的价格是 15 美元和 20 美元。

条件为 if daysAhead >= 10 的两个选项。

我花了几个小时试图解决这个问题，我需要帮助。

票证.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)";
    }
  }
}

最后的问题是...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

当您为 StudentAdvanceTicket 调用 getPrice() 时，您的程序实际上是从 AdvanceTicket 调用实现，它将返回 $30 或 $40。

现在，当您为 StudentAdvanceTicket 调用 toString() 时，它会从 super 调用 toString，它是用于 AdvanceTicket 的那个，那个调用对象的 getPrice() 方法，同样，它只返回 $30 或 $40 并且不使用 >price 成员变量。

正确的解决方案是覆盖 StudentAdvanceTicket 类的 getPrice。在该方法中，您调用 super.getPrice()，然后用它进行价格操作。