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Apache Commons Lang, a package of Java utility classes for the classes that are in java.lang's hierarchy, or are considered to be so standard as to justify existence in java.lang. The code is tested using the latest revision of the JDK for supported LTS releases: 8, 11, 17 and 21 currently. See https://github.com/apache/commons-lang/blob/master/.github/workflows/maven.yml Please ensure your build environment is up-to-date and kindly report any build issues.

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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()}.
 *
 * The calculation of the differences is consistent with equals 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}.
 *
 * 
 * {@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:
 * 
 *  * Assert.assertEquals(expected.diff(result), expected, result);
 * 
 *
 * @param  the type of objects that this object may be differentiated against
 * @since 3.3
 */
@FunctionalInterface
public interface Diffable {

    /**
     * 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 diff(T obj);
}