In need of customized JTextField

Question

I need to create a custom textfield, and the formatter won't cut it. I need to have formatting applied real time, with a variable number of characters. The ATM might be a good example, where you enter numbers and the display field fills in from left to right, with the decimal point and dollar sign always being in the correct location, the entry of a decimal point is optional, and comas appear as necessary as the number of digits to the left of the decimal point increases.
I have similar needs for percentage, and a few other value types. Currently I've extended PlainDocument and have it working, but I'm far from happy with the results, and wasn't able to make it abstract enough to be easily usable for slightly different formats.
Has anybody seen a component like this floating around? I would hate to recreate what somebody else has already done, particularly of the later effort has resulted in a better solution.
Thanks,
-Dave

Answer 1

does it have to be a textField?Yes - the users are quite adamant and and specific regarding the requirements for this field.
At first glance, your single replaceAll statement looks much simpler than what I've worked out. I think that some of the extra leg work I'm doing may not be necessary, but I do need to figure out where to insert numbers (in case of entry mid field), where deletions occur, where to place the character after updates, etc.
I'm posted what I've come up with below. I'm not happy with it - am still looking for the right solution, which I must have glossed right over.
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.text.NumberFormat;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;
public class TestTextField {
     public static void main(String[] args) {
          JTextField myTextField = new JTextField();
          myTextField.setHorizontalAlignment(JTextField.RIGHT);
          myTextField.setDocument(new UpperCaseDocument(myTextField));
          JFrame frame = new JFrame();
          frame.getContentPane().setLayout(new GridLayout(3, 1));
          frame.getContentPane().add(myTextField);
          frame.pack();
          frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
          frame.setVisible(true);
class UpperCaseDocument extends PlainDocument{
     StringBuffer contents;
     JTextField tf;
     public UpperCaseDocument(JTextField tf) {
          this.tf = tf;
          contents = new StringBuffer();
          contents.append("000");
          try {
               super.insertString(0, NumberFormat.getCurrencyInstance().format(0),
                         null);
          } catch (BadLocationException e) {
               // TODO Auto-generated catch block
               e.printStackTrace();
     public void insertString(int offs, String str, AttributeSet a)
               throws BadLocationException {
          if (str == null) {
               return;
          boolean allNumbers = isNumeric(str);
          if (allNumbers) {
               int offset = calcOffset(offs);
               contents.insert(offset, str);
               padContents();
               set(a);
               int caret = calcCaret(offset + str.length());
               System.out.println("C: " + caret);
               tf.setCaretPosition(caret);
          } else {
               Toolkit.getDefaultToolkit().beep();
     public void remove(int offs, int len) throws BadLocationException {
          super.remove(offs, len);
          String s = getText(0, getLength());
          s = replace(s, "$", "", -1);
          s = replace(s, ",", "", -1);
          s = replace(s, ".", "", -1);
          contents.replace(0, contents.length(), s);
          set(null);
          padContents();
          tf.setCaretPosition(offs);
     private void set(AttributeSet a) {
          try {
               String s1 = contents.substring(0, contents.length() - 2);
               String s2 = contents.substring(contents.length() - 2);
               String amount = s1 + "." + s2;
               double d = Double.parseDouble(amount);
               String curr = NumberFormat.getCurrencyInstance().format(d);
               super.remove(0, getLength());
               super.insertString(0, curr, a);
          } catch (Exception e) {
               // TODO Auto-generated catch block
               e.printStackTrace();
     public static String replace(String text, String repl, String with, int max) {
          if (text == null || with == null || max == 0) {
               return text;
          StringBuffer buf = new StringBuffer(text.length());
          int start = 0, end = 0;
          while ((end = text.indexOf(repl, start)) != -1) {
               buf.append(text.substring(start, end)).append(with);
               start = end + repl.length();
               if (--max == 0) {
                    break;
          buf.append(text.substring(start));
          return buf.toString();
     private int calcOffset(int offset) {
          // Take 1 off the top to accomodate for dollar sign
          if (offset > 0) {
               offset--;
          int numCommas = (contents.length() - 2) / 3;
          if (numCommas > 0 && (contents.length() - 2) % 3 == 0) {
               numCommas--;
          int prefix = (contents.length() - 2) % 3;
          if (prefix == 0) {
               prefix = 3;
          int commaShift = 0;
          for (int i = numCommas; i > 0; i--) {
               if (offset > prefix) {
                    commaShift++;
                    prefix += 4;
               } else {
                    break;
          offset -= commaShift;
          int secret = contents.length() + 1 - 2;
          if (offset > secret) {
               offset--;
          return offset;
     private int calcCaret(int offset) {
          if (offset > contents.length()) {
               System.out.println("oops");
               return getLength();
          // Take 1 off the top to accomodate for dollar sign
          if (offset > 0) {
               offset++;
          int numCommas = (contents.length() - 2) / 3;
          if (numCommas > 0 && (contents.length() - 2) % 3 == 0) {
               numCommas--;
          int prefix = (contents.length() - 2) % 3;
          if (prefix == 0) {
               prefix = 3;
          int commaShift = 0;
          for (int i = numCommas; i > 0; i--) {
               if (offset > prefix) {
                    commaShift++;
                    prefix += 3;
               } else {
                    break;
          offset += commaShift;
          int secret = getLength() - 2;
          if (offset > secret) {
               offset++;
          return offset;
     private void padContents() {
          if (contents.length() < 3) {
               int pading = 3 - contents.length();
               for (int i = 0; i < pading; i++) {
                    contents.insert(0, "0");
          } else {
               int excess = contents.length() - 3;
               for (int i = 0; i < excess; i++) {
                    if (contents.charAt(0) == '0') {
                         contents.deleteCharAt(0);
                    } else {
                         break;
     public static boolean isNumeric(String str) {
          if (str == null) {
               return false;
          int sz = str.length();
          for (int i = 0; i < sz; i++) {
               if (Character.isDigit(str.charAt(i)) == false) {
                    return false;
          return true;
}