001/*
002 * (C) Copyright 2006-2011 Nuxeo SA (http://nuxeo.com/) and others.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 * 
016 * Contributors:
017 *     Nuxeo - initial API and implementation
018 *
019 * $Id: ArrayUtils.java 28607 2008-01-09 15:49:32Z sfermigier $
020 */
021
022package org.nuxeo.common.utils;
023
024import java.lang.reflect.Array;
025import java.util.ArrayList;
026import java.util.Arrays;
027import java.util.HashSet;
028import java.util.List;
029import java.util.Set;
030
031/**
032 * Array utils.
033 *
034 * @author <a href="mailto:[email protected]">Julien Anguenot</a>
035 */
036@SuppressWarnings({ "SuppressionAnnotation" })
037public final class ArrayUtils {
038
039    // This is an utility class.
040    private ArrayUtils() {
041    }
042
043    /**
044     * Merges any number of Array.
045     * <p>
046     * Comes from : http://forum.java.sun.com/thread.jspa?threadID=202127&messageID=676603
047     *
048     * @param arrays several arrays
049     * @return a merged array
050     */
051    @SuppressWarnings("unchecked")
052    public static <T> T[] arrayMerge(T[]... arrays) {
053        int count = 0;
054        Class<?> klass = null;
055        for (T[] array : arrays) {
056            count += array.length;
057            if (klass == null && array.length > 0) {
058                klass = array[0].getClass();
059            }
060        }
061        if (count == 0) {
062            // all arrays are empty, return the first one
063            return arrays[0];
064        }
065        // create new array
066        T[] rv = (T[]) Array.newInstance(klass, count);
067        int start = 0;
068        for (T[] array : arrays) {
069            System.arraycopy(array, 0, rv, start, array.length);
070            start += array.length;
071        }
072        return rv;
073    }
074
075    /**
076     * Method for intersecting arrays elements. Copy of the first array and remove progressively elements if not found
077     * in the other arrays.
078     * <p>
079     * This method will keep the initial order of elements (as found in the first array).
080     */
081    @SuppressWarnings("unchecked")
082    public static <T> T[] intersect(final T[]... arrays) {
083        final Class type = arrays.getClass().getComponentType().getComponentType();
084        if (arrays.length == 0) {
085            return (T[]) Array.newInstance(type, 0);
086        }
087
088        final List<T> commonItems = new ArrayList<>();
089
090        final T[] firstArray = arrays[0];
091        commonItems.addAll(Arrays.asList(firstArray));
092
093        // check with the other arrays
094        // we skip the first array
095        for (int i = 1; i < arrays.length; i++) {
096            final T[] array = arrays[i];
097
098            final List<T> arrayAsList = Arrays.asList(array);
099
100            final Set<T> itemsToRemove = new HashSet<>();
101            for (T item : commonItems) {
102                if (!arrayAsList.contains(item)) {
103                    itemsToRemove.add(item);
104                }
105            }
106
107            commonItems.removeAll(itemsToRemove);
108        }
109
110        T[] result = (T[]) Array.newInstance(type, commonItems.size());
111        result = commonItems.toArray(result);
112
113        return result;
114    }
115
116}