textArea.getDocument().addDocumentListener(new MyDocumentListener());

    class MyDocumentListener implements DocumentListener {

        public void insertUpdate(DocumentEvent e) {
            Document doc =  (Document)e.getDocument();
            int loc = e.getOffset();
            System.out.print("location = " + loc + "\n");
            try {
                System.out.print("string = "+ doc.getText(loc, 1) + "\n");
            } catch (BadLocationException e1) {
                e1.printStackTrace();
            }
        }

        @Override
        public void removeUpdate(DocumentEvent e) {
            Document doc =  (Document)e.getDocument();
            int loc = e.getOffset();
            int e_length = e.getLength();
            int del_loc_end = loc + e_length - 1;
            if(e_length == 1) {
                System.out.print("delete " + loc + "\n");
            }else{
                System.out.print("delete " + loc + " to " + del_loc_end + "\n");
            }
        }

        @Override
        public void changedUpdate(DocumentEvent e) {
        }


    }