JTextField limiting character amount input and accepting numeric only

Question

here\'s the code that i have on how to limit the character input length

class JTextFieldLimit extends PlainDocument {
  private int limit;
  // optional uppe         


        

Answer 1

JFormattedTextField

 JTextComponent txt = new JFormattedTextField( new LimitedIntegerFormatter(limit) );
  txt.addPropertyChangeListener("value", yourPropertyChangeListener);


import javax.swing.text.DefaultFormatter;
import java.text.ParseException;

public class LimitedIntegerFormatter extends DefaultFormatter {

  static final long serialVersionUID = 1l;
  private int limit;

  public LimitedIntegerFormatter( int limit ) {
    this.limit = limit;
    setValueClass(Integer.class);
    setAllowsInvalid(false);
    setCommitsOnValidEdit(true);
  }
  @Override
  public Object stringToValue(String string) throws ParseException {
    if (string.equals("")) return null;
    if (string.length() > limit) throw new ParseException(string, limit);
    return super.stringToValue(string);
  }
}

yourPropertyChangeListener will be called with

new PropertyChangeEvent( "value", Integer oldValue, Integer newValue )

( oldValue or newValue will be null in "" text case )

after every valid edit