Java Collection Difference getIntersectAndDiffs(Collection a, Collection b, Comparator comparator)

Description

Returns a three-element array of mutable List s:

the intersection of a and b
the a - b difference
the b - a difference

License

Open Source License

Parameter

Parameter	Description
comparator	a comparator to sort results, or null to remain unsorted

Declaration

public static <T> List<T>[] getIntersectAndDiffs(Collection<? extends T> a, Collection<? extends T> b,
        Comparator<T> comparator) 

Method Source Code

//package com.java2s;
/*/*from w w w.  j a v  a 2  s  .  co  m*/
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

import java.util.*;

public class Main {
    /**
     * Returns a three-element array of mutable {@code List}s:
     * <ol>
     *    </li>
     *      the intersection of {@code a} and {@code b}
     *    <li>
     *    </li>
     *      the {@code a} - {@code b} difference
     *    <li>
     *    </li>
     *      the {@code b} - {@code a} difference
     *    <li>
     * </ol>
     *
     * @param       comparator
     *          a comparator to sort results, or {@code null} to remain
     *          unsorted
     */
    public static <T> List<T>[] getIntersectAndDiffs(Collection<? extends T> a, Collection<? extends T> b,
            Comparator<T> comparator) {

        int aSize = a.size();
        List<T> aDiff = new ArrayList<T>(aSize);
        aDiff.addAll(a);

        int bSize = b.size();
        List<T> bDiff = new ArrayList<T>(bSize);
        bDiff.addAll(b);

        if (comparator != null) {
            Collections.sort(aDiff, comparator);
            Collections.sort(bDiff, comparator);
        }

        List<T> abInter = new ArrayList<T>(Math.min(aSize, bSize));

        for (int i = aDiff.size() - 1; i >= 0; i--) {
            T element = aDiff.get(i);

            int index = comparator == null ? bDiff.indexOf(element)
                    : Collections.binarySearch(bDiff, element, comparator);

            if (index != -1) {
                bDiff.remove(index);
                aDiff.remove(i);
                abInter.add(element);
            }
        }

        @SuppressWarnings({ "unchecked" })
        List<T>[] array = (List<T>[]) new List[] { abInter, aDiff, bDiff };

        return array;
    }

    public static <T> void addAll(Collection<T> collection, T... array) {
        for (T t : array) {
            collection.add(t);
        }
    }
}

Related

1. difference(Collection collection1, Collection result, Collection collection2)
2. difference(Collection a, Collection b)
3. difference(final Collection c1, final Collection c2)
4. difference(final Collection c1, final Collection c2)
5. differentNull(Collection collection)
6. getSymmetricDifference(final Set firstCollection, final Set secondCollection)
7. leftDifference(final Collection c1, final Collection c2)