/guava/guava/src/com/google/common/eventbus/EventBus.java
this.executor = checkNotNull ( executor ) ;
EventBus( String identifier, Executor executor, Dispatcher dispatcher, SubscriberExceptionHandler exceptionHandler) { this.identifier = checkNotNull(identifier); <extra_id_0> this.dispatcher = checkNotNull(dispatcher); this.exceptionHandler = checkNotNull(exceptionHandler); } public final String identifier() { return identifier; }