hashCode function that properly handles arrays, collections, maps, collections of arrays, and maps of arrays. - Android java.util

Android examples for java.util:Map

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Description

hashCode function that properly handles arrays, collections, maps, collections of arrays, and maps of arrays.

Demo Code

/*//ww w.j a  v  a2 s . c o  m
 * --------------------
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2008-2009 Sun Microsystems, Inc. All rights reserved.
 *
 * The contents of this file are subject to the terms of the Common Development
 * and Distribution License("CDDL") (the "License").  You may not use this file
 * except in compliance with the License.
 *
 * You can obtain a copy of the License at
 * http://opensource.org/licenses/cddl1.php
 * See the License for the specific language governing permissions and limitations
 * under the License.
 *
 * When distributing the Covered Code, include this CDDL Header Notice in each file
 * and include the License file at http://opensource.org/licenses/cddl1.php.
 * If applicable, add the following below this CDDL Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyrighted [year] [name of copyright owner]"
 * --------------------
 */
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;

public class Main{
    public static void main(String[] argv){
        Object o = "book2s.com";
        System.out.println(hashCode(o));
    }
    /**
     * hashCode function that properly handles arrays, collections, maps,
     * collections of arrays, and maps of arrays.
     *
     * @param o
     *            The object. May be null.
     * @return the hashCode
     */
    public static int hashCode(Object o) {
        if (o == null) {
            return 0;
        } else if (o.getClass().isArray()) {
            int length = Array.getLength(o);
            int rv = 0;
            for (int i = 0; i < length; i++) {
                Object el = Array.get(o, i);
                rv += CollectionUtil.hashCode(el);
            }
            return rv;
        } else if (o instanceof Collection) {
            Collection<?> l = (Collection<?>) o;
            int rv = 0;
            for (Object el : l) {
                rv += CollectionUtil.hashCode(el);
            }
            return rv;
        } else if (o instanceof Map) {
            Map<?, ?> map = (Map<?, ?>) o;
            return CollectionUtil.hashCode(map.values());
        } else {
            return o.hashCode();
        }
    }
}

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