/src/main/java/org/htmlunit/WebClientInternals.java
if ( listeners_ != null) {
if ( listeners_ == null ) {
public class WebClientInternals implements Serializable { private Collection<Listener> listeners_; WebClientInternals() { } public void addListener(final Listener listener) { synchronized (this) { <extra_id_0> listeners_ = Collections.synchronizedList(new ArrayList<>()); } } listeners_.add(listener); } public void removeListener(final Listener listener) {