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The Amazon Web Services SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2010-2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Portions copyright 2006-2009 James Murty. Please see LICENSE.txt
 * for applicable license terms and NOTICE.txt for applicable notices.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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 com.amazonaws.util;

/**
 * Classes related utilities.
 */
public enum Classes {
    ;
    /**
     * Returns the class of the immediate subclass of the given parent class for
     * the given object instance; or null if such immediate subclass cannot be
     * uniquely identified for the given object instance.
     * 
     * @param parentClass
     *            the parent class. The child class is {@link Object} if and
     *            only if the parent class is null.
     * @param instance
     *            the given object instance
     */
    public static Class childClassOf(Class parentClass,
            Object instance) {
        if (instance == null || instance == Object.class)
            return null;
        if (parentClass != null) {
            if (parentClass.isInterface()) {
                // child of an interface class is not injective (ie one-to-one)
                return null;
            }
        }
        Class childClass = instance.getClass();
        while (true) {
            Class parent = childClass.getSuperclass();
            if (parent == parentClass)
                return childClass;
            if (parent == null)
                return null;
            childClass = parent;
        }
    }
}