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.
/**
 * 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;

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
 */
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 diff(T obj);
}