Check for empty JFormattedTextField

Question

I'm new here, and I'd like some help on a small Java project I'm doing. This is the code snippet I need help with:

private void CalculateButtonActionPerformed(java.awt.event.ActionEvent evt)                                                
{                                                    
    // TODO add your handling code here:
    float Principal, Rate, Time, Result, Temp;

    Principal = Float.valueOf(PrincipalTextField.getText());
    Rate = Float.valueOf(RateTextField.getText());
    Time = Float.valueOf(TimeTextField.getText());

    Temp = (float) Math.pow((1 + Rate / 100), Time);
    Result = Principal * Temp;
    ResultTextField.setText(String.valueOf(Result));
}

I'd like to check if PrincipalTextField, OR RateTextField, OR TimeTextField aren't filled by the user, and if so, display a dialog box that asks him/her to recheck them. The text fields are JFormattedTextField variables. I realise that I can do this with a if/else or a while loop, but I'm not sure how to set about doing so. Please help!

Sujay · Answer 1 · 2012-09-07T09:08:01.613

You can do something like this:

The getText() returns you a String value. So you can always invoke length() and check whether the length comes to 0 or not. (*I would suggest calling trim() on the String before calling length() to remove any whitespaces)
Next if any of the length comes to be zero, what you want to do is display a Dialog Box. This you can do by calling JOptionPane.showMessageDialog(). You can read more about "How to Make Dialogs" over here.

So, you would do something like this:

String principalText = PrincipalTextField.getText();
String rateText = RateTextField.getText();
String timeText = TimeTextField.getText();

if(principalText.trim().length == 0 || rateText.trim().length == 0 || timeText.trim().length == 0){
    JOptionPane.showMessageDialog(null, "YOUR_ERROR_MSG", "ERROR_TITLE", JOptionPane.ERROR_MESSAGE);
}

This might be off-topic, but I would suggest looking at Java Naming Convention. The convention for variables is to compose variable names using mixed case letters starting with a lower case letter

Ah, thank you. I had experimented with the trim() and length() methods, but it seems that I didn't use them properly. The thing about naming convention is new... Isn't it only methods that start with lower case letters and then uppercase, as in "showMessageDialog"? I'm also learning Objective-C, where variables are capitalised the way I've done it. Maybe I just got confused. But thank you very much. — SRSR333, Sep 08 '12 at 15:16
@user1654223: Nope, variables also follow the same pattern. But glad to help :) — Sujay, Sep 08 '12 at 15:18

score 2 · Answer 2 · answered Sep 07 '12 at 09:05

you miss reason for why there is JFormattedTextField
have to set Number Formatter for JFormattedTextField, then
- you not need to parsing Float value (better could be to use double)
- empty coudl be 0 (zero) value by default
- take value in the form ((Number)PrincipalTextField.getValue()).floatValue();
look at code example for tutorial,

score 1 · Answer 3 · edited May 23 '17 at 12:30

1

Also consider subclassing InputVerifier, as discussed in Validating Input. There's a related example here.

edited May 23 '17 at 12:30

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answered Sep 07 '12 at 10:58

trashgod

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Check for empty JFormattedTextField

3 Answers3