Again, many thanks! I should have sought help this morning before wasting all day stumbling around in the dark.
Just for my future reference here's what ended up working for me:
public void displayJButtonActionPerformed(ActionEvent click)
{
String age=ageJTextField.getText();
int ageNumber = Integer.parseInt( age );
if ( ageNumber >= 8 && ageNumber < 13 )
{
displayJLabel.setText("Goosebumps books are the best!");
}
else if (ageNumber >= 13 && ageNumber < 18)
{
displayJLabel.setText ("No Dating allowed!");
}
else if (ageNumber >= 18 && ageNumber <30)
{
displayJLabel.setText ("Best years of my life!");
}
}