Mask in a JTextField

Question

How I set a mask (for example for a date) in a JTextField??? I think that I can make it using a Document, but how???
Thanks in advance!!!

Answer 1

First sorry for one mistake: TextDocument is not a standard class, the right one is PlainDocument.
Here is an example:
public class TextDocument extends PlainDocument{
    protected int characterLimit = 10;
     private int firstDayDigit = 0;
     public TextDocument() {
          this(10);
     public TextDocument(int limit) {
          super();
          characterLimit = limit;
      * Process the input from the user and check for the
      * right numbers.
     public void insertString(int offset, String str, AttributeSet attrib) throws BadLocationException {
          if(offset == 0 && !str.equals("00.00.0000")){
               try{
                    firstDayDigit = Integer.parseInt(str);
               }catch(NumberFormatException nfe){
                    Toolkit.getDefaultToolkit().beep();
                    return;
          if(!str.equals("00.00.0000")){
               try{
                    int digit = Integer.parseInt(str);
               }catch(NumberFormatException nfe){
                    str = "0";
          if(str.length() == 1) {
               switch(offset){
                    case 0:
                         //check for the correct day
                         if(Integer.parseInt(str) > 3){
                              str = "0";
                         removeIt(offset, str, attrib);
                         break;
                    case 1:
                         if(firstDayDigit == 3){
                              if(Integer.parseInt(str) > 1){
                                   str = "0";
                         removeIt(offset, str, attrib);
                         break;
                    case 3:
                         //check for the correct month
                         if(Integer.parseInt(str) > 1){
                              str = "0";
                         removeIt(offset, str, attrib);
                         break;
                    case 6:
                         //check for the correct year
                         if(Integer.parseInt(str) != 2){
                              str = "2";
                         removeIt(offset, str, attrib);
                         break;
                    case 4:
                    case 7:
                    case 8:
                    case 9:
                         removeIt(offset, str, attrib);
                         break;
                    case 2:
                        // user did not type in a '-'
                        if(!str.equals(".")) {
                              // remove the '.' if there is one
                              try{
                                   remove(offset, 1);
                              }catch(BadLocationException ble){
                                   // don't throw back to calling method
                              // insert another '.'
                              super.insertString(offset, ".", attrib);
                              // remove the next character in the field
                              try {
                                   remove(offset + 1, 1);
                              } catch(BadLocationException ble) {
                                   // don't throw back to calling method
                              if(Integer.parseInt(str) > 1){
                                   str = "0";
                              // insert the new character in it's place
                              super.insertString(offset + 1, str, attrib);
                         } else {
                              // user did type in a '.', remove the old on
                              try {
                                   remove(offset, 1);
                              } catch(BadLocationException ble){
                                   // don't throw back to calling method
                              // and insert a new one
                              super.insertString(offset, str, attrib);
                         break;
                    case 5:
                        // user did not type in a '.'
                        if(!str.equals(".")) {
                              // remove the '.' if there is one
                              try{
                                   remove(offset, 1);
                              }catch(BadLocationException ble){
                                   // don't throw back to calling method
                              // insert another '.'
                              super.insertString(offset, ".", attrib);
                              // remove the next character in the field
                              try {
                                   remove(offset + 1, 1);
                              } catch(BadLocationException ble) {
                                   // don't throw back to calling method
                              if(Integer.parseInt(str) != 2){
                                   str = "2";
                              // insert the new character in it's place
                              super.insertString(offset + 1, str, attrib);
                         } else {
                              // user did type in a '.', remove the old on
                              try {
                                   remove(offset, 1);
                              } catch(BadLocationException ble){
                                   // don't throw back to calling method
                              // and insert a new one
                              super.insertString(offset, str, attrib);
                         break;
                    default:
                         throw new BadLocationException("Limit of " + characterLimit + " characters.", offset);
          } else {
               for(int i = offset; i < offset + str.length(); i++) {
                    insertString(i, ""+ str.charAt(i), attrib);
     protected void removeIt(int offset, String str, AttributeSet attrib) throws BadLocationException{
          try {
               remove(offset, 1);
          }catch(BadLocationException ble) {
          super.insertString(offset, str, attrib);
}