com.liferay.portal.kernel.security.RandomUtil.java Source code

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Here is the source code for com.liferay.portal.kernel.security.RandomUtil.java

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/**
 * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 *
 * This library 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 Lesser General Public License for more
 * details.
 */

package com.liferay.portal.kernel.security;

import java.util.Random;

/**
 * @author Shuyang Zhou
 */
public class RandomUtil {

    public static int nextInt(int n) {
        return random.nextInt(n);
    }

    public static int[] nextInts(int n, int size) {
        if (size > n) {
            size = n;
        }

        int[] numbers = new int[n];

        for (int i = 0; i < n; i++) {
            numbers[i] = i;
        }

        shuffle(random, numbers);

        if (size == n) {
            return numbers;
        }

        int[] results = new int[size];

        System.arraycopy(numbers, 0, results, 0, size);

        return results;
    }

    public static void shuffle(Random random, int[] numbers) {
        for (int i = numbers.length; i > 1; i--) {
            int position = random.nextInt(i);

            if (position != (i - 1)) {
                int number = numbers[position];

                numbers[position] = numbers[i - 1];
                numbers[i - 1] = number;
            }
        }
    }

    public static String shuffle(Random random, String s) {
        StringBuilder sb = new StringBuilder(s);

        shuffle(random, sb);

        return sb.toString();
    }

    public static void shuffle(Random random, StringBuilder sb) {
        for (int i = sb.length(); i > 1; i--) {
            int position = random.nextInt(i);

            if (position != (i - 1)) {
                char c = sb.charAt(position);

                sb.setCharAt(position, sb.charAt(i - 1));
                sb.setCharAt(i - 1, c);
            }
        }
    }

    public static String shuffle(String s) {
        return shuffle(random, s);
    }

    protected static Random random = new Random();

}