Try with keyListener in your textfield
jTextField.addKeyListener(new KeyListener() {
@Override
public void keyTyped(KeyEvent e) {
}
@Override
public void keyPressed(KeyEvent e) {
if (text.getText().length() >= 1) {
button.setEnabled(true);
} else {
button.setEnabled(false);
}
}
@Override
public void keyReleased(KeyEvent e) {
}
});