well im sure there are set methods for the JTextfield class..
but you could create your own.
like...
public void increaseSize(JTextfield t) { // im not sure how to aquire the old size so you can increase by // how ever much you need to..
}
but somthing along those lines
then you could have a method called
public void checkForNumbers(JTextfield t) { String A = t.getText();
for(int i = 0; i<A.length(); i++) { //again i don't know what syntax to use. // but you have to compare each char at A.charAt(i); // to see if it is an integer or not. } }