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Thread: Integer.parseInt problem

  1. #1
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    Default Integer.parseInt problem

    Hi guys, working through the Deitel Java book and am stumped on one of the cases they give, with no examples, I've tried Googling around but with no success.
    The program is just a simple GUI to solve a math problem but the task mentions using the parseInt functio which I can't seem to get to work.
    Below is kind of what I've been trying...

    Any help much appreciated

    import javax.swing.JOptionPane;
     
    public class Exercise
     
    {
     
    public static void main( String[] args )
     
    {
     
    int	number1;
    int	number2;
    int	sum;
     
     
    String number1 = JOptionPane.showInputDialog( "Enter first number:" );
    //number1 = Integer.parseInt();
     
    String number2 = JOptionPane.showInputDialog( "Enter second number:" );
    //number2 = Integer.parseInt();
     
    sum = number1 + number2;
     
    String message = String.format( "Sum of numbers is %d", sum );
     
    JOptionPane.showMessageDialog( null, message );
     
    }
     
    }


  2. #2
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    Default Re: Integer.parseInt problem

    1. You can't have both an integer and a String called number1, same for number2.

    2. Integer.parseInt(); takes parameters, which means you must give the method something to parse into an int.

    3. Why are you using the String message? You can put whatever you like directly into the message dialog.

    If these tips don't help you out, let me know, I'll explain further. However, keep in mind that figuring it out yourself means you understand it better and you will remember it.

    edit: You should really be putting try catch statements on your input dialogues, because if I entered letters into them, your program would crash.

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    3therk1ll (June 28th, 2013)

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    Default Re: Integer.parseInt problem

    Thanks for the reply dude.
    I am using the string message because I thought the idea was to read a string and filter out the integers from that string.
    Not using catch because I'm just working my way through the Deitel Java Programming book and haven't been introduced to catch statements yet, the exercise was to take a previous basic math command line program and convert it to be used with a basic GUI.
    Java is still really new to me, I've only ever scripted before with Bash.

    I think I have it a bit more figured out now, but I am still doing something wrong as I get an error:

    C:\Program Files\Java\jdk1.7.0_21\bin>javac C:\Java\Exercise.java
    C:\Java\Exercise.java:20: error: incompatible types
    sum = number1 + number2;
                  ^
      required: int
      found:    String
    1 error

    This is my code thus far, I assume that it is still expecting a string and won't do addition with two strings, something wrong with how I'm parsing?
    I tried changing String number1 and 2 to int but just got more errors.

    import javax.swing.JOptionPane;
     
    public class Exercise
     
    {
     
    public static void main( String[] args )
     
    {
     
    int	sum;
     
     
    String number1 = JOptionPane.showInputDialog( "Enter first number:" );
    Integer.parseInt( number1 );
     
    String number2 = JOptionPane.showInputDialog( "Enter second number:" );
    Integer.parseInt( number2 );
     
    sum = number1 + number2;
     
    String message = String.format( "Sum of numbers is %d", sum );
     
    JOptionPane.showMessageDialog( null, message );
     
    }
     
    }

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    Senior Member PhHein's Avatar
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    Default Re: Integer.parseInt problem

    parseInt returns what? Do you expect it to automagically transform a String into an int?

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    Default Re: Integer.parseInt problem

    I thought the point of it was to parse a string for integers.

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    Default Re: Integer.parseInt problem

    Yes, and what happens with the parsed int?

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    3therk1ll (June 28th, 2013)

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    Default Re: Integer.parseInt problem

    Urgh, I'm a dick, I got it now, cheers for the help, I wasn't declaring turning the parsed string into another variable and declaring it as an int.

    String number1 = JOptionPane.showInputDialog( "Enter first number:" );
    int number1a = Integer.parseInt( number1 );

    That worked.

  10. #8
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    Default Re: Integer.parseInt problem

    No problem Don't forget the Exception handling, as has been mentioned before.

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    Default Re: Integer.parseInt problem

    Urgh, I'm a dick, I got it now, cheers for the help, I wasn't declaring turning the parsed string into another variable and declaring it as an int.

    String number1 = JOptionPane.showInputDialog( "Enter first number:" );
    int number1a = Integer.parseInt( number1 );

    That worked.

    --- Update ---

    Yeah ok thanks dude.
    Sorry about the double post, the page won't let me edit my posts, tried to repost with code tags.

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