Java List Random Item nextRandomElement(final List list)

Description

Returns the next random element from the given Collection

License

Open Source License

Return

list

Declaration

private static <T> T nextRandomElement(final List<T> list) 

Method Source Code

//package com.java2s;
/**//from  ww  w.ja v  a2  s .c o  m
 * ShortPasta Foundation
 * http://www.shortpasta.org
 * Copyright 2009 and beyond, Sal Ingrilli at the ShortPasta Software Foundation
 * <p/>
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License version 3
 * as published by the Free Software Foundation as long as:
 * 1. You credit the original author somewhere within your product or website
 * 2. The credit is easily reachable and not burried deep
 * 3. Your end-user can easily see it
 * 4. You register your name (optional) and company/group/org name (required)
 * at http://www.shortpasta.org
 * 5. You do all of the above within 4 weeks of integrating this software
 * 6. You contribute feedback, fixes, and requests for features
 * <p/>
 * If/when you derive a commercial gain from using this software
 * please donate at http://www.shortpasta.org
 * <p/>
 * If prefer or require, contact the author specified above to:
 * 1. Release you from the above requirements
 * 2. Acquire a commercial license
 * 3. Purchase a support contract
 * 4. Request a different license
 * 5. Anything else
 * <p/>
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, similarly
 * to how this is described in the GNU Lesser General Public License.
 * <p/>
 * User: Sal Ingrilli
 * Date: Oct 9, 2014
 * Time: 6:58:48 PM
 */

import java.util.List;
import java.util.Random;

public class Main {
    private static final Random random = new Random();

    /**
     * Returns the next random element from the given Collection
     * @return list
     */
    private static <T> T nextRandomElement(final List<T> list) {

        // preconditions: array cannot be empty, otherwise we would have to return null, in which
        // case the caller would not be able to tell whether the element returned is a valid element or not
        if (list.size() == 0) {
            throw new RuntimeException("list.size () must be > 0");
        }

        // randomize the next
        final int lowerBound = 0;
        final int upperBound = list.size();
        final int index = lowerBound
                + random.nextInt(upperBound - lowerBound);
        return list.get(index);
    }
}

Related

1. newRandom(int size, int price, List oldRandomList)
2. newRandomIntegerList(int size)
3. newRandomStringList(int size, String... strings)
4. newRandomV1(int size, int price, List oldRandomList)
5. nextElement(List list)
6. pickNAtRandom(List vals, int n, long seed)
7. pickOneAtRandom(List list)
8. PickRandom(final Collection list)
9. pickRandom(LinkedList list, int n)