/*
 * Java Genetic Algorithm Library (@__identifier__@).
 * Copyright (c) @__year__@ Franz Wilhelmstötter
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Author:
 *    Franz Wilhelmstötter (franz.wilhelmstoetter@gmx.at)
 */
package org.jenetics;

import static java.lang.String.format;
import static java.util.Objects.requireNonNull;
import static java.util.stream.Collectors.maxBy;

import java.io.Serializable;
import java.util.Random;
import java.util.stream.IntStream;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
import javax.xml.bind.annotation.adapters.XmlAdapter;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

import org.jenetics.internal.util.Equality;
import org.jenetics.internal.util.Hash;

import org.jenetics.util.RandomRegistry;

/**
 * In tournament selection the best individual from a random sample of <i>s</i>
 * individuals is chosen from the population <i>P<sub>g</sub></i>. The samples
 * are drawn with replacement. An individual will win a tournament only if its
 * fitness is greater than the fitness of the other <i>s-1</i>  competitors.
 * Note that the worst individual never survives, and the best individual wins
 * in all the tournaments it participates. The selection pressure can be varied
 * by changing the tournament size <i>s</i> . For large values of <i>s</i>, weak
 * individuals have less chance being selected.
 *
 * @see <a href="http://en.wikipedia.org/wiki/Tournament_selection">Tournament selection</a>
 *
 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
 * @since 1.0
 * @version !__version__!
 */
@XmlJavaTypeAdapter(TournamentSelector.Model.Adapter.class)
public class TournamentSelector<
	G extends Gene<?, G>,
	C extends Comparable<? super C>
>
	implements Selector<G, C>, Serializable
{

	private static final long serialVersionUID = 1L;

	private final int _sampleSize;

	/**
	 * Create a tournament selector with the give sample size. The sample size
	 * must be greater than one.
	 *
	 * @param sampleSize the number of individuals involved in one tournament
	 * @throws IllegalArgumentException if the sample size is smaller than two.
	 */
	public TournamentSelector(final int sampleSize) {
		if (sampleSize < 2) {
			throw new IllegalArgumentException(
				"Sample size must be greater than one, but was " + sampleSize
			);
		}
		_sampleSize = sampleSize;
	}

	/**
	 * Create a tournament selector with sample size two.
	 */
	public TournamentSelector() {
		this(2);
	}

	@Override
	public Population<G, C> select(
		final Population<G, C> population,
		final int count,
		final Optimize opt
	) {
		requireNonNull(population, "Population");
		requireNonNull(opt, "Optimization");
		if (count < 0) {
			throw new IllegalArgumentException(format(
				"Selection count must be greater or equal then zero, but was %s",
				count
			));
		}

		final Random random = RandomRegistry.getRandom();
		return population.isEmpty()
			? new Population<>(0)
			: new Population<G, C>(count)
				.fill(() -> select(population, opt, _sampleSize, random), count);
	}

	private Phenotype<G, C> select(
		final Population<G, C> population,
		final Optimize opt,
		final int sampleSize,
		final Random random
	) {
		final int N = population.size();
		return IntStream.range(0, sampleSize)
			.mapToObj(i -> population.get(random.nextInt(N)))
			.collect(maxBy(opt.ascending())).get();
	}

	@Override
	public int hashCode() {
		return Hash.of(getClass()).and(_sampleSize).value();
	}

	@Override
	public boolean equals(final Object obj) {
		return Equality.of(this, obj).test(s -> _sampleSize == s._sampleSize);
	}

	@Override
	public String toString() {
		return format("%s[s=%d]", getClass().getSimpleName(), _sampleSize);
	}


	/* *************************************************************************
	 *  JAXB object serialization
	 * ************************************************************************/

	@XmlRootElement(name = "tournament-selector")
	@XmlType(name = "org.jenetics.TournamentSelector")
	@XmlAccessorType(XmlAccessType.FIELD)
	@SuppressWarnings({"unchecked", "rawtypes"})
	final static class Model {

		@XmlAttribute(name = "samples", required = true)
		public int samples;

		public final static class Adapter
			extends XmlAdapter<Model, TournamentSelector>
		{
			@Override
			public Model marshal(final TournamentSelector value) {
				final Model m = new Model();
				m.samples = value._sampleSize;
				return m;
			}

			@Override
			public TournamentSelector unmarshal(final Model m) {
				return new TournamentSelector(m.samples);
			}
		}
	}

}

@@ -3176,24 +3176,204 @@
 his(2);%0A%09%7D%0A%0A
+%09/**%0A%09 * Return the sample size of the tournament selector.%0A%09 *%0A%09 * @return the sample size of the tournament selector%0A%09 */%0A%09public int getSampleSize() %7B%0A%09%09return _sampleSize;%0A%09%7D%0A%0A
 %09@Override%0A%09

Add getter for TournamentSelector.sampleSize property.