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.List;
034
035/**
036 * A read-only view on a list with a set of indices from the
037 * underlying list that must be accepted; all other
038 * indices are discarded. The view is
039 * continuous, and presents itself without any gaps.
040 * The size of the view is equal to the length of 
041 * the number of skipped elements. 
042 * <p>
043 * The {@link AcceptingListView} is the exact opposite
044 * of the {@link SkippingListView}. 
045 * 
046 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
047 *
048 * @param <T> The type of element in the list
049 */
050public class AcceptingListView<T> extends AbstractList<T> {
051        private List<T> list;
052        private int[] indices;
053
054        /**
055         * Construct with the underlying list and a set of
056         * indices for the view. 
057         * 
058         * @param list the backing list
059         * @param indices the indices
060         */
061        public AcceptingListView(List<T> list, int... indices) {
062                this.list = list;
063
064                if (indices == null)
065                        indices = new int[0];
066                
067                this.indices = indices;
068        }
069        
070        @Override
071        public T get(int index) {
072                return list.get(indices[index]);
073        }
074
075        @Override
076        public int size() {
077                return indices.length;
078        }
079}