Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.configuration2.event; /** * <p> * Definition of a generic event listener interface. * </p> * <p> * This event listener interface is used throughout the * <em>Commons Configuration</em> library for reacting on all kinds of supported * events. The interface is pretty minimalistic, defining only a single * {@code onEvent()} method. This simplifies the implementation of custom event * listeners and also supports the new language features introduced with Java 8 * ({@code EventListener} is a functional interface and thus can be represented * by a Lambda expression). * </p> * * @version $Id$ * @since 2.0 * @param <T> the type of events this listener can process */ public interface EventListener<T extends Event> { /** * Notifies this event listener about the arrival of a new event. Typically, * event listeners are registered at an event source providing an * {@link EventType}. This event type acts as a filter; all events matched * by the filter are passed to the listener. The type parameters defined by * the {@code EventType} class and this interface guarantee that the events * delivered to the handler are compatible with the concrete method * signature of {@code onEvent()}. * * @param event the event */ void onEvent(T event); }