001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.util.list;
031
032import java.util.AbstractList;
033import java.util.ArrayList;
034import java.util.List;
035
036/**
037 * A read-only {@link List} view built on top of a list of underlying lists.
038 * Useful for combining multiple lists without the memory overhead of actually
039 * creating new storage for all the elements.
040 * <p>
041 * Be aware that if you change the underlying lists, then those changes will be
042 * reflected in this list.
043 * 
044 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
045 * 
046 * @param <T>
047 */
048public class ConcatenatedList<T> extends AbstractList<T> {
049        private List<List<T>> innerLists = new ArrayList<List<T>>();
050
051        /**
052         * Construct with the given list of lists.
053         * 
054         * @param lists
055         *            the lists
056         */
057        public ConcatenatedList(List<List<T>> lists) {
058                innerLists = lists;
059        }
060
061        /**
062         * Construct with the given lists.
063         * 
064         * @param l1
065         *            first list
066         * @param l2
067         *            second list
068         */
069        public ConcatenatedList(List<T> l1, List<T> l2) {
070                innerLists.add(l1);
071                innerLists.add(l2);
072        }
073
074        /**
075         * Construct with the given lists.
076         * 
077         * @param l1
078         *            first list
079         * @param l2
080         *            second list
081         * @param l3
082         *            third list
083         */
084        public ConcatenatedList(List<T> l1, List<T> l2, List<T> l3) {
085                innerLists.add(l1);
086                innerLists.add(l2);
087                innerLists.add(l3);
088        }
089
090        /**
091         * Construct with the given lists.
092         * 
093         * @param l1
094         *            first list
095         * @param l2
096         *            second list
097         * @param l3
098         *            third list
099         * @param l4
100         *            forth list
101         */
102        public ConcatenatedList(List<T> l1, List<T> l2, List<T> l3, List<T> l4) {
103                innerLists.add(l1);
104                innerLists.add(l2);
105                innerLists.add(l3);
106                innerLists.add(l4);
107        }
108
109        @Override
110        public T get(int index) {
111                if (index < 0)
112                        throw new IndexOutOfBoundsException();
113
114                int count = 0;
115
116                for (final List<T> d : innerLists) {
117                        if (index >= count + d.size()) {
118                                count += d.size();
119                        } else {
120                                return d.get(index - count);
121                        }
122                }
123
124                throw new IndexOutOfBoundsException();
125        }
126
127        @Override
128        public int size() {
129                int size = 0;
130                for (final List<T> d : innerLists) {
131                        size += d.size();
132                }
133                return size;
134        }
135}