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Various functions for performing general functions
There is a newer version: 1.20.0
/*
 * The MIT License
 *
 * Copyright 2021 Takashi Harano
 *
 * 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 com.libutil;

import java.security.SecureRandom;

/**
 * Generates random values.
 */
public class RandomGenerator {

  private static SecureRandom r = new SecureRandom();

  /**
   * Returns a random integer value.
   *
   * @return a random integer value
   */
  public static int getInt() {
    return r.nextInt();
  }

  /**
   * Returns a random integer value.
   *
   * @param max
   *          the max value
   * @return a random integer value between 0 to max
   */
  public static int getInt(int max) {
    return r.nextInt(max + 1);
  }

  /**
   * Returns a random integer value.
   *
   * @param min
   *          the minimum value
   * @param max
   *          the maximum value
   * @return a random integer value between min to max
   */
  public static int getInt(int min, int max) {
    int i;
    max++;
    do {
      i = r.nextInt(max);
    } while (i < min);
    return i;
  }

  /**
   * Returns a random long value.
   *
   * @return a random long value
   */
  public static long getLong() {
    return r.nextLong();
  }

  /**
   * Returns a random float value.

   * e.g., 0.017796695
   *
   * @return a random float value between 0.0 to 1.0
   */
  public static float getFloat() {
    return r.nextFloat();
  }

  /**
   * Returns a random double value.

   * e.g., 0.8697886198087033
   *
   * @return a random double value between 0.0 to 1.0
   */
  public static double getDouble() {
    return r.nextDouble();
  }

  /**
   * Returns a random boolean value
   *
   * @return true or false
   */
  public static boolean getBoolean() {
    return r.nextBoolean();
  }

  /**
   * Returns a random character value
   *
   * @return a random character value between 0 to 0xFFFF
   */
  public static char getChar() {
    return (char) getInt(0, 0xFFFF);
  }

  /**
   * Returns a random character value
   *
   * @param min
   *          the minimum value
   * @param max
   *          the maximum value
   * @return a random character value between min to max
   */
  public static char getChar(int min, int max) {
    if (min > max) {
      int w = min;
      max = min;
      min = w;
    }
    if (min < 0) {
      min = 0;
    }
    if (max > 0xFFFF) {
      max = 0xFFFF;
    }
    return (char) getInt(min, max);
  }

  /**
   * Returns a random string.

   * 

   * getString("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789",
   * 8);

   * out: "TWEQWhq2"
   * 
   * @param chars
   *          characters to use
   * @param len
   *          length of the output
   * @return a randomly-generated string
   */
  public static String getString(String chars, int len) {
    char[] cTable = chars.toCharArray();
    int lastIdx = cTable.length - 1;
    char[] buf = new char[len];
    for (int i = 0; i < len; i++) {
      int idx = r.nextInt(lastIdx + 1);
      buf[i] = cTable[idx];
    }
    String ret = new String(buf);
    return ret;
  }

}