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  1. #1
    Join Date
    Jul 2007

    please help regarding focus


    catch (NumberFormatException error) // catch to identify if integers were not inputs in JTextFields
    // give an error box if periodicPayment, interest, compunds, and years have String inputs
    JOptionPane.showMessageDialog( this,
    "Please enter numbers for Periodic Payment and Interest,\n" +
    "and integers for Compounds per Year and Years. Try again!",
    "Input Error", JOptionPane.ERROR_MESSAGE );

    // transfer focus

    } // end catch

    My question is:

    How to make the focus on the place where we have wrong problems? I want to use if, else statement, but, in this case, how to validate string inputs?


  2. #2
    Join Date
    Dec 2004
    San Bernardino County, California
    I am uncertain about what you mean by your use of the word "focus". I imagine that the erroneously formatted data would not be added to your storage container because of the exception. I am not sure if you are using focus in the "GUI focus" - "active window" - manner, or just "calling attention to the input which generated the exception". I proceed with the second in mind.

    The key to your approach to validation lies where your exception is being generated.

    I expect that you have assigned the input to some temporary variable(s). As long as you have not deleted or overwritten those variables (or they have not gone out of scope) you can still evaluate them.

    Do your validation on the values stored in these variables - use a "Pattern" and "Matcher" to test whether this validates [see the Regex materials]. OR, if it is as easy as the input string cannot evaluate to a number because of the presence of a non-number character, your test is straightforward. Just display the user's erroneous input back to him/her and ask the user to re-enter the input in the correct format.

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