The java.awt.TextField could be monitored for changes by adding a TextListener for TextEvent's. In the JTextComponent based components, changes are broadcasted from the model via a DocumentEvent to DocumentListeners. The DocumentEvent gives the location of the change and the kind of change if desired. The code fragment might look something like:
DocumentListener myListener = ??;
JTextField myArea = ??;
myArea.getDocument().addDocumentListener(myListene r);