Using a DocumentListener makes other components dissapear.

Question

I was wanting to use a DocumentListener to cut down on some code but when I used it all the buttons and TextFields dissapeared. Just wondering if anyone has had the same problem. Here is some of the code.
// Only activate the button if there are more than 3 letters
Document doc = lettersField.getDocument();
doc.addDocumentListener(new MyDocumentListener());
Document doc2 = addField.getDocument();
doc2.addDocumentListener(new MyDocumentListener());
class MyDocumentListener implemets DocumentListener {
JButton = tempButton;
Document = tempDoc;
public MyDocumentListener() {
if(letters.hasFocus() ) {
tempButton = letters;
tempDoc = lettersField.getDocument();
} else if (addWord.hasFocus() ) {
tempButton = addWord;
tempDoc = addField.getDocument();
public void insertUpdate(DocumentEvent e) {
try {
if( (tempDoc.getText(0, tempDoc.getLength()) ).length() >= 3) {
tempButton.setEnabled(true);
} catch (BadLocationException badLoc) {
// Deactivate the button when there are less than 3 letters
public void removeUpdate(DocumentEvent e) {
try {
if( (tempDoc.getText(0, tempDoc.getLength()) ).length() < 3) {
tempButton.setEnabled(false);
} catch (BadLocationException badLoc) {
public void changedUpdate(DocumentEvent e) { }
}

Answer 1

First of all the first two lines of your MyDocumentListener class won't compile ("JButton = tempButton"? What's that supposed to mean?)
Second, the constructor for that class is testing whether certain fields have the focus. That only happens when you create the MyDocumentListener, so what's the point?
Mind-reading time again. I am guessing you want to associate a JButton with each instance of the listener, so that the listener can enable and disable it as necessary. So, do this:class MyDocumentListener implements DocumentListener {
  JButton associatedButton;
  public MyDocumentListener(JButton theButton) {
    associatedButton = theButton;
}Note that I didn't tell the MyDocumentListener what Document it was listening to. I don't have to do that because DocumentEvent has a getDocument() method that tells me that for each event. So use this as one of the methods in MyDocumentListener:public void insertUpdate(DocumentEvent e) {
  Document doc = e.getDocument();
  try {
    if(doc.getLength() >= 3){
// sorry about the >, it's supposed to be the greater-than symbol but it won't come out that way.
      associatedButton.setEnabled(true);
  } catch (BadLocationException badLoc) {
}Finally, in your main program do this to assign the listeners to the fields:lettersField.getDocument().addDocumentListener(new MyDocumentListener(letters));
addField.getDocument().addDocumentListener(new MyDocumentListener(addWord));