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;
031
032import java.util.Collection;
033import java.util.List;
034
035/**
036 * Interface defining an object capable of sampling a collection.
037 * 
038 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
039 * 
040 * @param <T>
041 *            type of items in the collection being sampled
042 */
043public interface CollectionSampler<T> {
044        /**
045         * Set the items to sample from. This should only be called once for any
046         * given set of items. Implementors can assume that calling this resets any
047         * state of the sampler.
048         * 
049         * @param collection
050         *            the items to sample from
051         */
052        public void setCollection(Collection<? extends T> collection);
053
054        /**
055         * Samples <code>nItems</code> items from the collection set by
056         * {@link #setCollection(Collection)}, returning a new collection with the
057         * given samples. Implementations can decide what to do if
058         * <code>nItems</code> is bigger than the number of items in the collection.
059         * 
060         * @param nItems
061         *            the number of items to sample
062         * @return the sample; can be <code>null</code> if a sample cannot be made
063         *         for any reason.
064         */
065        public List<T> sample(int nItems);
066}