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 * 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
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 * 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
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package org.apache.commons.lang3.builder;

Diffable classes can be compared with other objects for differences. The DiffResult object retrieved can be queried for a list of differences or printed using the DiffResult.toString().
The calculation of the differences is consistent with equals if and only if d1.equals(d2) implies d1.diff(d2) == "". It is strongly recommended that implementations are consistent with equals to avoid confusion. Note that null is not an instance of any class and d1.diff(null) should throw a NullPointerException.
 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);

Type parameters:
<T> – the type of objects that this object may be differentiated against
Since:
3.3/**
 * <p>{@code 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>
 *
 * <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 {@code NullPointerException}.</p>
 *
 * <p>
 * {@code 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.
Params:
obj – the object to diff against, can be null
Throws:
NullPointerException – if the specified object is null
Returns:
a list of differences/**
     * <p>Retrieves a list of the differences between
     * this object and the supplied object.</p>
     *
     * @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);
}