/*
 * Copyright (c) 2006-2009 Philipp Meinen <philipp@bind.ch>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the Software
 * is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH
 * THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package ch.bind.philib;

import java.util.Random;

/**
 * Various functions for dealing with arrays which are not present in the
 * standard {@link java.util.Arrays} class.
 * 
 * @author Philipp Meinen
 * @since 2009-06-10
 */
public final class PhiArrays {

	private PhiArrays() {
	}

	private static final Random rand = new Random(); // TODO: thread-safe?

	/**
	 * Fills the <code>destination</code> array with randomly picked values from
	 * the <code>source</code> array. No value will be picked twice.
	 * 
	 * @param source
	 *            The array from which random values must be picked. The content
	 *            of this array will not be altered.
	 * @param destination
	 *            The array which must be filled with random values. Previous
	 *            values within this array will be overwritten.
	 * @throws NullPointerException
	 *             If either of the two parameters is null.
	 * @throws IllegalArgumentException
	 *             If the <code>source</code>-array is smaller then the
	 *             <code>destination</code>-array.
	 */
	public static <T> void pickRandom(final T[] source, final T[] destination) {
		if (source == null)
			throw new NullPointerException("the source array must not be null");
		if (destination == null)
			throw new NullPointerException(
					"the destination array must not be null");
		final int nSrc = source.length;
		final int nDst = destination.length;
		if (nSrc < nDst)
			throw new IllegalArgumentException(
					"the source arrays length must be greater or equal to the destination arrays length");
		final boolean[] taken = new boolean[nSrc];

		for (int i = 0; i < nDst; i++) {
			int idx = rand.nextInt(nSrc);
			while (taken[idx])
				idx = rand.nextInt(nSrc);
			taken[idx] = true;
			destination[i] = source[idx];
		}
	}

}

/*
 * Copyright (c) 2006-2009 Philipp Meinen <philipp@bind.ch>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the Software
 * is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH
 * THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package ch.bind.philib;

import java.util.Random;

/**
 * Various functions for dealing with arrays which are not present in the
 * standard {@link java.util.Arrays} class.
 * 
 * @author Philipp Meinen
 * @since 2009-06-10
 */
public final class PhiArrays {

	private PhiArrays() {
	}

	// java.util.Random is updated atomically => this is thread-safe
	private static final Random rand = new Random();

	/**
	 * Fills the <code>destination</code> array with randomly picked values from
	 * the <code>source</code> array. No value will be picked twice.
	 * 
	 * @param source
	 *            The array from which random values must be picked. The content
	 *            of this array will not be altered.
	 * @param destination
	 *            The array which must be filled with random values. Previous
	 *            values within this array will be overwritten.
	 * @throws NullPointerException
	 *             If either of the two parameters is null.
	 * @throws IllegalArgumentException
	 *             If the <code>source</code>-array is smaller then the
	 *             <code>destination</code>-array.
	 */
	public static <T> void pickRandom(final T[] source, final T[] destination) {
		if (source == null)
			throw new NullPointerException("the source array must not be null");
		if (destination == null)
			throw new NullPointerException(
					"the destination array must not be null");
		final int nSrc = source.length;
		final int nDst = destination.length;
		if (nSrc < nDst)
			throw new IllegalArgumentException(
					"the source arrays length must be greater or equal to the destination arrays length");
		final boolean[] taken = new boolean[nSrc];

		for (int i = 0; i < nDst; i++) {
			int idx = rand.nextInt(nSrc);
			while (taken[idx])
				idx = rand.nextInt(nSrc);
			taken[idx] = true;
			destination[i] = source[idx];
		}
	}

}

update thread-safety comment