Java Collection Random Element pickOneRandomly(Collection from)

Description

bad performance don't use for large sets use collections.shuffle and remove last

License

Open Source License

Parameter

Parameter	Description
from	a parameter

Declaration

public static String pickOneRandomly(Collection<String> from) 

Method Source Code

//package com.java2s;
/**/*from  www  .j  av  a  2s.  c  o m*/
 * Copyright (C) 2007-2011, Jens Lehmann
 *
 * This file is part of DL-Learner.
 *
 * DL-Learner is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * DL-Learner 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.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

import java.util.Collection;
import java.util.Random;

public class Main {
    /**
     * bad performance don't use for large sets
     * use collections.shuffle and remove last
     * @param from
     * @return
     */
    public static String pickOneRandomly(Collection<String> from) {
        //      Monitor m =  JamonMonitorLogger.getTimeMonitor(ExMakerHelper.class, "bad_performance").start();

        if (from.isEmpty()) {
            return null;
        }
        Random r = new Random();
        String[] array = from.toArray(new String[] {});

        int index = Math.round((float) (array.length * r.nextFloat()));
        //      m.stop();
        try {
            return array[index];
        } catch (Exception e) {
            return pickOneRandomly(from);
        }
    }
}

Related

1. getRandom(Collection collection)
2. getRandomNumber(Collection collection, int number)
3. nextItem(Collection items, Random random)
4. oneOf(Collection array)
5. peekRandom(Collection collection, Random rnd)
6. pollRandom(Collection collection, Random rnd)
7. random(Collection collection)
8. random(Collection coll)
9. random(Collection coll)