Question

我是java的新手，在尝试使用bluej创建一个售票机后，我真的不知道该怎么办。

 public class CarParkTicketMachine
{
    private double RunningBalance;
    private double CurrentBalance;
    private String CarReg;
    private static double MinTicketCharge = 0.7;

    //Constructor
    public CarParkTicketMachine()
    {
        RunningBalance = 0;
        CurrentBalance = 0;
    }

    //Try and request a ticket
    public void RequestTick()
    {
        if(Validate())
        {
            //Create a ticket for the customer
            CarParkTicket ticket = new CarParkTicket (CarReg, CurrentBalance);
            //keep a running total
            RunningBalance += CurrentBalance;
            //clear the customer's balance
            CurrentBalance = 0;
            //print ticket for the customer
            ticket.PrintTicket();
        }
    }

    //Perform check to ensure we can purchase a ticket
    private boolean Validate()
    {
        boolean valid = false;

        //Check that the user has entered their car registration
        if(!(CarReg == null || CarReg.isEmpty())) //must NOT be null
        {
            //Check that the user has entered enough money
            if(CurrentBalance >= MinTicketCharge)
            {
                return true;
            }
            else
            {
                System.out.println("You have not entered enough money");
            }
        }
        else
        {
            System.out.println("Please enter your car registration");
        }
        return false;
    }
}

public class CarParkTicket
{
    //Customer's Car Registration
    private String CarRegistration; 
   //Cost of the ticket
   private double charge;

   public CarParkTicket (String CarReg, double charge)
   {
       CarRegistration = CarReg;
       double Charge = charge;
    }

    public void PrintTicket()
    {
        System.out.println("*****************");
        System.out.println("Your Ticket");
        System.out.println("Registration:" + CarRegistration);
        System.out.println("Cost: £" + charge );
        System.out.println("*****************");
    }
}

public class Coin
{
    //property to hold the value of the coin
    private double Value;

    //Constructor
    public Coin(double value)
    {
        this.Value = value;
    }

    //accessor
    public double GetValue()
    {
        return Value;
    }
}

我的三个类编译时没有任何问题但是当我创建一个'CarParkTicketMachine'的新对象并尝试输入一个方法调用来设置汽车注册或插入一个硬币我得到一个'错误：找不到符号 - 变量。

我觉得问题出在这一部分，但是因为我对java / bluej非常新，我真的不知道如何解决这个问题：

private Boolean Validate()
    {
        boolean valid = false;

        //Check that the user has entered their car registration
        if(CarReg == (" "))
        {
            //Check that the user has entered enough money
            if(CurrentBalance >= MinTicketCharge)
            {
                valid = true;
            }
            else
            {System.out.println("You have not entered enough money");
            }
        }
        else
        {
            System.out.println("Please enter your car registration");
        }
        return valid;
    }

Answer 1

以下是我对Validate（）的建议：请注意，您正在尝试检查用户是否已输入＆＃34; ＆＃34;然后检查输入的现金。但是你需要确保用户没有输入＆＃34; ＆＃34; （这意味着他输入了一个或一个名字）

private bool Validate()
{

    //Check that the user has entered their car registration
    if(!(CarReg == null || CarReg.isEmpty())) // must NOT be null
    {
        //Check that the user has entered enough money
        if(CurrentBalance >= MinTicketCharge)
        {
            return true;
        }
        else
        {
          System.out.println("You have not entered enough money");
        }
    }
    else
    {
        System.out.println("Please enter your car registration");
    }
    return false;
}

编辑：我应该告诉你，在＆＃34;返回true＆＃34;之后，该方法停止执行。因此，当您不返回true时（这意味着现金的if语句不为真），该方法将返回到返回false的末尾。

您可以使用所谓的＆＃34; tenary operator＆＃34;来缩短if语句。

这应该是这样的：

return CurrentBalance >= MinTicketCharge ? true : false;

你的if语句和你的回报在一行。

BlueJ错误：不兼容的类型：int无法转换为java.lang.String（Ticket Machine Simulation）

1 个答案: