Java List Random Item sampleWithoutReplacement(List items, int sampleSize)

Description

sample Without Replacement

License

Apache License

Declaration

public static <T> List<T> sampleWithoutReplacement(List<T> items, int sampleSize) 

Method Source Code

//package com.java2s;
/*******************************************************************************
 * Copyright 2014 Observational Health Data Sciences and Informatics
 * /*from  ww w .  jav  a  2  s .  co m*/
 * This file is part of WhiteRabbit
 * 
 * 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.
 ******************************************************************************/

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

public class Main {
    public static <T> List<T> sampleWithoutReplacement(List<T> items, int sampleSize) {
        if (sampleSize > items.size()) {
            return items;
        }
        Random random = new Random();
        List<T> sample = new ArrayList<T>();
        for (int i = 0; i < sampleSize; i++)
            sample.add(items.remove(random.nextInt(items.size())));
        return sample;
    }

    public static int[] sampleWithoutReplacement(int minValue, int maxValue, int sampleSize) {
        if (sampleSize > (maxValue - minValue + 1)) {
            int[] sample = new int[maxValue - minValue + 1];
            for (int i = minValue; i <= maxValue; i++)
                sample[i - minValue] = i;
            return sample;
        } else {
            Random random = new Random();
            int[] sample = new int[sampleSize];
            for (int i = 0; i < sampleSize; i++) {
                int number = random.nextInt(maxValue - minValue + 1);
                while (contains(sample, number))
                    number = random.nextInt(maxValue - minValue + 1);
                sample[i] = number;
            }
            return sample;
        }

    }

    private static boolean contains(int[] sample, int number) {
        for (int i : sample)
            if (i == number)
                return true;
        return false;
    }
}

Related

1. pickupFromList(String[] list)
2. resampleWithReplacement(final List l, final int n)
3. sample(List l, Random r)
4. sample(Random random, List list)
5. sampleRandomSublist(List list, int sampleSize)
6. sampleWithReplacement(final Random random, final List data, final int sampleSize)
7. sampleWithReplacementInto(final Random random, final List data, final int sampleSize, final Collection result)
8. softMaxIndex(Random rand, int listSize, double temperature)