ui/src/main/java/ucar/util/prefs/ui/PrefPanel.java
public void addActionListener(ActionListener l) {
    listenerList.add(java.awt.event.ActionListener.class, l);
  }
public void addActionListener(ActionListener l) {
    listenerList.add(java.awt.event.ActionListener.class, l);
  }
public void addActionListener ( ActionListener l ) { listenerList . add ( java . awt . event . ActionListener . class , l ) ; }
Add listener: action event sent if "apply" button is pressed
Add listener : action event sent if apply button is pressed