Limit the no. of char in the JTextfield

Question

I want to limit the number charecters in the JTextfield during the time of typing the charecters. How can I do it simply ? One way, I can make an own class extend the JTextfield and check by using the events to restrict the charecters. Other than this simply how can I do it ?
advance thanx
Goban

Answer 1

Here's an simple and easy solution using PlainDocument. It gives a beep sound if the user tries to enter text after the specified length.
textField.setDocument( new TextFieldVerifier() );
class TextFieldVerifier extends PlainDocument {
int requiredLength = 10; // whatever length you want
public void insertString( int offset, String str, AttributeSet attSet ) throws BadLocationException {
boolean valid = true;
if (str == null) {
return;
String old = getText( 0, getLength() );
/* insert the new string at the given offset, into the old string */
String newStr = old.substring( 0, offset ) + str + old.substring( offset );
if (newStr.length() > requiredLength)
valid = false;
Toolkit.getDefaultToolkit().beep();
if ( valid )
super.insertString( offset, str, attSet );
}