001/** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.lang3.builder; 018 019/** 020 * <p>{@code Diffable} classes can be compared with other objects 021 * for differences. The {@link DiffResult} object retrieved can be queried 022 * for a list of differences or printed using the {@link DiffResult#toString()}.</p> 023 * 024 * <p>The calculation of the differences is <i>consistent with equals</i> if 025 * and only if {@code d1.equals(d2)} implies {@code d1.diff(d2) == ""}. 026 * It is strongly recommended that implementations are consistent with equals 027 * to avoid confusion. Note that {@code null} is not an instance of any class 028 * and {@code d1.diff(null)} should throw a {@code NullPointerException}.</p> 029 * 030 * <p> 031 * {@code Diffable} classes lend themselves well to unit testing, in which a 032 * easily readable description of the differences between an anticipated result and 033 * an actual result can be retrieved. For example: 034 * </p> 035 * <pre> 036 * Assert.assertEquals(expected.diff(result), expected, result); 037 * </pre> 038 * 039 * @param <T> the type of objects that this object may be differentiated against 040 * @since 3.3 041 * @version $Id: Diffable.java 1561225 2014-01-24 23:17:29Z djones $ 042 */ 043public interface Diffable<T> { 044 045 /** 046 * <p>Retrieves a list of the differences between 047 * this object and the supplied object.</p> 048 * 049 * @param obj the object to diff against, can be {@code null} 050 * @return a list of differences 051 * @throws NullPointerException if the specified object is {@code null} 052 */ 053 DiffResult diff(T obj); 054}