Regain focus on FormattedTextField when message displayed...

Question

Hello,
I have a formatted text field that takes a mask formatter in the form of "####"
People should fill in a number between 0-9999.
However, when the focus is put on the next field (a radio button ic), I want to display a messagedialog saying "Please fill in the number" when nothing is filled in.
So far, so good.
NOW I would like the formatted textfield to automatically regain the focus after the user has pressed "OK" in the message dialog...
I have tried putting a requestFocus() right after the messagedialog-code, but then it repeats the message dialog 3 times (requiring to click ok three times) and only then it puts the focus on the text field again...
Any ideas to make sure the focus is regained after one click?
(So basically I want to oblige the person to fill in the first field...(and some others!))
Thank you

Answer 1

This is the code:
(don't pay attention to the messy coding rules...I suck at those...) (plus just beginning to program here...)
public void jdesiredCalFormattedTextField_focusLost(java.awt.event.
FocusEvent e)
String cal=new String(jdesiredCalFormattedTextField.getText());
cal=cal.trim();
jdesiredCalFormattedTextField.setValue(cal);
if (jdesiredCalFormattedTextField.getText().trim().length()==0)
JOptionPane.showMessageDialog(
null,
"Gelieve gewenst aantal calorieen in te vullen.",
"Calorieen foutief!",
JOptionPane.ERROR_MESSAGE);
jdesiredCalFormattedTextField.requestFocus();
else
jSchemeResultDesiredCalLabel.setText(cal);
jDesiredResultsOverviewResCalLabel.setText(cal);
so it checks whether the field is empty (trimmed length==0), if so, it gives the messagedialog, and after the messagedialog it requests focus again...
Using Java 1.4.2_04
thnx
Wouter