Please HELP Java small program

[afrttoh]

Hello there,
I need to do a small program which is:

Write a program called ShoppingCalculator.java that allows the user to
enter the prices of several items they have bought and then tells them the
total amount. The user can enter the prices for as many items as they
want, until they click Cancel. The program should then output the total
amount they spent, in a message dialog box. Use pounds for all the
amounts.

Unfortunately, after spending many hours trying to figure out how to make this programme work correctly! I couldn’t.
I guess it’s because I am a very beginner at java programming :-)
I would really appreciate it if you could help me out.
Thanks

Here is what I have done so far:

import javax.swing.JOptionPane;
 
 
public class ShoppingCalculator
 
{
 
 
    public static void main(String[] args)
        {
 
            boolean done = false;
            double amount;
            String input;
            double total = 0;
 
            while (!done)
                {
                    input = JOptionPane.showInputDialog("Enter the amount you spent on the next item:");
                    amount = Double.parseDouble (input);
           {
           if (input == null)total = total + amount;         
       }           
 
 
               JOptionPane.showMessageDialog (null, "You spent a total amound of " + total  );
                }
        }
}

[jack239]

I could see you've written

 if(input == null) total = total + amount

I think it should be

 if(input != null) total = total + amount

because you'll add amount to total if and only if input has some value and not null

[Eranga]

Actually you should deal with the input, null check.

    public static void main(String[] args) {
        
        double amount = 0.0;
        
        while(true) {
            String str = JOptionPane.showInputDialog(null, "Enter the value");
            if(str != null) {
                amount += Double.parseDouble(str);
            }
            else
                break;
        }
        
        JOptionPane.showMessageDialog(null, "Amount is " + amount);
    }

[CJSLMAN]

I have some comments on your usage of curly brackets (or is it braces?)... anyway...

          {
           if (input == null)total = total + amount;         
       }

• The {} above, don't do anything (not needed, unless I missed their purpose)
• Always use {} for if-else statements when (even if) it's a one-liner. This way you can always add code to your if-else statements without having to worry about remembering to add the {}.

Luck,
CJSL

[Eranga]

Always use {} for if-else statements when (even if) it's a one-liner. This way you can always add code to your if-else statements without having to worry about remembering to add the {}.

I give full credit on this. It's a good practice actually. I've miss that. But in later once you get more familiar with programming those kind of things, simply you can avoid those braces. So it gives much clear view on your code.

[afrttoh]

thank you so much , its working now ..:-)

[Eranga]

If you solve the problem please mark it as solved lol. It's really helpful to all other members.

[afrttoh]

Here it is fully working:

import javax.swing.JOptionPane;


public class ShoppingCalculator

{


public static void main(String[] args) {

double amount = 0.0;

while(true) {
String str = JOptionPane.showInputDialog(null, "Enter the value");
if(str != null) {
amount += Double.parseDouble(str);
}
else
break;
}

JOptionPane.showMessageDialog(null, "Amount is £" + amount);
}
}

Thanks alot Eranga :)

[Eranga]

Ya, that's what I explain in my code segment.

By the way, are you working on Notepad? Why are you not using line indent there? If you use it, much easy to read the code.

[afrttoh]

Ya, that's what I explain in my code segment.

By the way, are you working on Notepad? Why are you not using line indent there? If you use it, much easy to read the code.

I am using Editplus.
is the line indent better?

[Eranga]

I am using Editplus.
is the line indent better?

See the code segment I'm posting here. That's write on NetBeans and it has auto indenting facility. It's much easy to read, and it's much clear, isn't it?

[afrttoh]

yes , i think so , ill Google it and download it now .
thank you once aging you have been very helpful!

[Eranga]

ill Google it and download it now .

What you are going to download? NetBeans?

[afrttoh]

What you are going to download? NetBeans?

Yes ,is it free to use?

[Eranga]

Yep, it's free. If you want to work on with NetBeans download the latest version 6.1, there is another version 6.5 but it's a beta version.

Here is the download link,

Choose the correct one you need and download.

Actually for line indenting you need to use NetBeans, you can use Tab space for that in editplus. Only thing is you should have a clear idea how to put tab spaces correctly.