Android Collection Equal isEqualCollection(final Collection a, final Collection b)

Description

Returns true if the given java.util.Collections contain exactly the same elements with exactly the same cardinalities.

License

Apache License

Parameter

Parameter	Description
a	the first collection, must not be null
b	the second collection, must not be null

Return

if the collections contain the same elements with the same cardinalities.

Declaration

public static boolean isEqualCollection(final Collection<?> a,
        final Collection<?> b) 

Method Source Code

//package com.java2s;
/*/*  ww  w  .  j a va 2s  . c  o m*/
 * (C) Copyright Itude Mobile B.V., The Netherlands
 * 
 * Licensed 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.
 */

import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class Main {
    private static Integer INTEGER_ONE = new Integer(1);

    /**
     * Returns true if the given <i>java.util.Collections</i> contain exactly the same elements with exactly the same cardinalities.
     * That is, if the cardinality of e in a is equal to the cardinality of e in b, for each element e in a or b. 
     * 
     * @param a the first collection, must not be null
     * @param b the second collection, must not be null
     * @return if the collections contain the same elements with the same cardinalities.
     */
    public static boolean isEqualCollection(final Collection<?> a,
            final Collection<?> b) {

        if (a.size() != b.size()) {
            return false;

        } else {
            Map<?, ?> mapA = getCardinalityMap(a);
            Map<?, ?> mapB = getCardinalityMap(b);

            if (mapA.size() != mapB.size()) {
                return false;
            } else {
                Iterator<?> it = mapA.keySet().iterator();

                while (it.hasNext()) {
                    Object obj = it.next();
                    if (getFreq(obj, mapA) != getFreq(obj, mapB)) {
                        return false;
                    }
                }
                return true;
            }
        }
    }

    @SuppressWarnings("unchecked")
    public static Map<?, ?> getCardinalityMap(final Collection<?> coll) {
        Map count = new HashMap();

        for (Iterator<?> it = coll.iterator(); it.hasNext();) {
            Object obj = it.next();
            Integer c = (Integer) (count.get(obj));

            if (c == null) {
                count.put(obj, INTEGER_ONE);
            } else {
                count.put(obj, new Integer(c.intValue() + 1));
            }
        }
        return count;
    }

    private static final int getFreq(final Object obj,
            final Map<?, ?> freqMap) {
        Integer count = (Integer) freqMap.get(obj);
        return count != null ? count.intValue() : 0;
    }

    public static <T> T get(Iterable<T> collection, int idx) {
        Iterator<T> it = collection.iterator();
        T next = null;
        do {
            if (it.hasNext())
                next = it.next();
            else
                return null;
            idx--;
        } while (idx >= 0);
        return next;
    }
}