cdm/src/main/java/ucar/nc2/util/ListenerManager.java
public synchronized void addListener(Object l) {
    if (!listeners.contains(l)) {
      listeners.add(l);
      hasListeners = true;
    } else
      logger.warn("ListenerManager.addListener already has Listener " + l);
  }
public synchronized void addListener(Object l) {
    if (!listeners.contains(l)) {
      listeners.add(l);
      hasListeners = true;
    } else
      logger.warn("ListenerManager.addListener already has Listener " + l);
  }
Add a listener.

@param l listener must be of type "listener_class"