Java中的2个相同的类

Question

Hi!

I have a small design problem in my current project. I have a class that holds the information about the time a Customer was in a Shop.

public class Customer {
    private String enterTime;
    private String leaveTime;

    public void enterTimeToInt {
        Integer.parseInt(enterTime);
    } 

    public void leaveTimeToInt {
        Integer.parseInt(leaveTime);
    } 
}

Now, in my program, i came across a situation where i had to make sure if there was any customer in the shop at a given time. Now, what i did was that i made another instance of the Customer class, which represented the given time and then checked if it matches any "real" Customer. But the problem is though, that i made a customer object representing time in a more abstract sense, not a customer.

What should i do in this case? I need exactly the same methods and variables as the Customer class has, but i don't think it is a good design choice to just make a Customer class that represents random time, not a specific customer's time.

Thank you very much!

Answer 1

Now, what i did was that i made another instance of the Customer class, which represented the given time and then checked if it matches any "real" Customer.

That's not what you want to do.

What you want to do is go through each customer with one time, and see if that time is between the enterTime and leaveTime .

Edited to answer the question:

I agree that the class is badly named. The information is about a customer, so I named it CustomerVisit .

Your CustomerVisit class should look more like this:

import java.util.Calendar;

public class CustomerVisit {
    private Calendar enterTime;
    private Calendar leaveTime;


    public Calendar getEnterTime() {
        return enterTime;
    }

    public void setEnterTime(Calendar enterTime) {
        this.enterTime = enterTime;
    }

    public Calendar getLeaveTime() {
        return leaveTime;
    }

    public void setLeaveTime(Calendar leaveTime) {
        this.leaveTime = leaveTime;
    }

    public boolean isVisit(Calendar givenTime) {
        if (givenTime.after(enterTime) && givenTime.before(leaveTime)) {
            return true;
        } else {
            return false;
        }
    }

    public void setVisit(String visitString) {
        // File format is hh:mm-hh:mm
        String[] times = visitString.split("-");
        String[] enterTimeString = times[0].split(":");
        String[] leaveTimeString = times[1].split(":");

        enterTime = setCalendar(enterTimeString);
        leaveTime = setCalendar(leaveTimeString);
    }

    private Calendar setCalendar(String[] timeString) {
        Calendar calendar = Calendar.getInstance();
        calendar.set(Calendar.HOUR_OF_DAY, 
                Integer.valueOf(timeString[0]));
        calendar.set(Calendar.MINUTE, 
                Integer.valueOf(timeString[1]));
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MILLISECOND, 0);

        return calendar;
    }
}

Instead of storing the time as a String , you need to store it in an object made for date / time calculations, like Calendar .

I was working on adding a SimpleDateFormat so you can display the enterTime and the leaveTime as a String.

With the isVisit method, you can loop through your CustomerVisit instances, and see which customers, or how many customers, visited at the givenTime .

The setVisit method takes the String from the file, and converts the String to Calendar objects.

Answer 2

You should not need a new type of customer for this problem.

When you say time I presume you mean within a certain range. I would do something like this:

public class CustomerRange  
{  
     Collection<Customer> customers;  

     ...   

     public boolean customerInShop(Date time)  
     {  
            for(Customer customer : customers)  
            {  
                  if(customer.getStart().after(time) && customer.getEnd().before(time))  
                  {
                      return true;
                  }  
            }  
            return false;
     }   
}  

you need to update your Customer class like so:

public class Customer  
{  
     Date start;  
     Date end;  
       ...
}  

As it stands currently, you have a dangerous API and one that doesn't work:

public void enterTimeToInt {
        Integer.parseInt(enterTime);
    } 

One this doesn't return an int, which is what you most likely want to do. Also, you have not defensively coded against the case that enterTime is not a valid integer. Further most dates are treated as a long