JTextField eventos

[dogduck]

Código:

String memoria=jTextField1.getText();
....
jTextField1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jTextField1ActionPerformed(evt);
            }
        });
....
private void jTextField1ActionPerformed(java.awt.event.ActionEvent evt) {

       if (!memoria.equals(jTextField1.getText())){
         javax.swing.JOptionPane panel=null;
         panel.showMessageDialog(null,"ha cambiado el texto");
       
       }
    }