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

Description

Returns true iff the given Collection s contain exactly the same elements with exactly the same cardinality.

License

Apache License

Declaration

public static boolean isEqualCollection(final Collection a, final Collection b) 

Method Source Code

//package com.java2s;
/*//  w  w w.  ja v  a  2  s . com
 * Copyright 1999-2004 The Apache Software Foundation
 *
 * 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;
import java.util.NoSuchElementException;

public class Main {
    /**
     * Returns <tt>true</tt> iff the given {@link Collection}s contain exactly
     * the same elements with exactly the same cardinality.
     * <p>
     * That is, iff the cardinality of <i>e</i> in <i>a</i> is equal to the
     * cardinality of <i>e</i> in <i>b</i>, for each element <i>e</i> in
     * <i>a</i> or <i>b</i>.
     */
    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;
            }
        }
    }

    /**
     * Returns a {@link Map} mapping each unique element in the given
     * {@link Collection} to an {@link Integer} representing the number of
     * occurances of that element in the {@link Collection}. An entry that maps
     * to <tt>null</tt> indicates that the element does not appear in the given
     * {@link Collection}.
     */
    public static Map getCardinalityMap(final Collection col) {
        HashMap count = new HashMap();
        Iterator it = col.iterator();
        while (it.hasNext()) {
            Object obj = it.next();
            Integer c = (Integer) (count.get(obj));
            if (null == c) {
                count.put(obj, new Integer(1));
            } else {
                count.put(obj, new Integer(c.intValue() + 1));
            }
        }
        return count;
    }

    private static final int getFreq(final Object obj, final Map freqMap) {
        try {
            return ((Integer) (freqMap.get(obj))).intValue();
        } catch (NullPointerException e) {
            // ignored
        } catch (NoSuchElementException e) {
            // ignored
        }
        return 0;
    }
}

Related

1. isEqual(Collection left, Collection right)
2. isEqual(Collection one, Collection two)
3. isEqual(Collection coll, Comparator comp)
4. isEqual(Collection a, Collection b)
5. isEqualBasicCol(Collection col1, Collection col2)
6. isEqualCollection(final Collection a, final Collection b)
7. isEqualDeep(Collection a, Collection b)
8. isEquals(Collection set1, Collection set2)
9. isEqualsSize(Collection res, Collection des)