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/*
* 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.lang3.builder;
/**
* {@link Diffable} classes can be compared with other objects
* for differences. The {@link DiffResult} object retrieved can be queried
* for a list of differences or printed using the {@link DiffResult#toString()}.
*
* <p>The calculation of the differences is <i>consistent with equals</i> if
* and only if {@code d1.equals(d2)} implies {@code d1.diff(d2) == ""}.
* It is strongly recommended that implementations are consistent with equals
* to avoid confusion. Note that {@code null} is not an instance of any class
* and {@code d1.diff(null)} should throw a {@link NullPointerException}.</p>
*
* <p>
* {@link Diffable} classes lend themselves well to unit testing, in which a
* easily readable description of the differences between an anticipated result and
* an actual result can be retrieved. For example:
* </p>
* <pre>
* Assert.assertEquals(expected.diff(result), expected, result);
* </pre>
*
* @param <T> the type of objects that this object may be differentiated against
* @since 3.3
*/
@FunctionalInterface
public interface Diffable<T> {
/**
* Retrieves a list of the differences between
* this object and the supplied object.
*
* @param obj the object to diff against, can be {@code null}
* @return a list of differences
* @throws NullPointerException if the specified object is {@code null}
*/
DiffResult<T> diff(T obj);
}
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