public boolean addListener(ZooKeeperConnectionListener listener) {
		return this.listeners.add(listener);
	}
Add a {@link ZooKeeperConnectionListener}.

@param listener the listener to add
@return true if the listener was added or false if it was already registered
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/zookeeper/ZooKeeperConnection.java