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/**
* Description: For generating random numbers.
*
* Author Create/Modi Note
* Xiaofeng Xie Feb 22, 2001
*
* 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.
*
* Please acknowledge the author(s) if you use this code in any way.
*
* @version 1.0
* @Since MAOS1.0
*/
package net.adaptivebox.global;
import java.util.Random;
import java.security.SecureRandom;
public class RandomGenerator {
/**
* Pseudo-random number generator instance.
*/
private static Random PRNG = new Random();
/**
* Switch between weaker, but faster pseudo-random number generator and
* stronger, but slower.
*
* @param stronger activation of secure pseudo random generator flag
*/
public static void useStrongerGenerator(boolean stronger) {
if(stronger == true) {
PRNG = new SecureRandom();
} else {
PRNG = new Random();
}
}
/**
* This function returns a random integer number between the lowLimit and
* upLimit.
*
* @param lowLimit lower limits upLimit The upper limits (between which the
* random number is to be generated)
* @return int return value Example: for find [0,1,2]
*/
public static int intRangeRandom(int lowLimit, int upLimit) {
int num = lowLimit + PRNG.nextInt(upLimit - lowLimit + 1);
return num;
}
/**
* This function returns a random float number between the lowLimit and upLimit.
*
* @param lowLimit lower limits upLimit The upper limits (between which the
* random number is to be generated)
* @return double return value
*/
public static double doubleRangeRandom(double lowLimit, double upLimit) {
double num = lowLimit + PRNG.nextDouble() * (upLimit - lowLimit);
return num;
}
/**
* This function returns a random float number between the zero (inclusive) and one (exclusive).
*
* @return double value in the range [0, 1)
*/
public static double doubleZeroOneRandom() {
return PRNG.nextDouble();
}
public static int[] randomSelection(int maxNum, int times) {
if (maxNum < 0) {
maxNum = 0;
}
if (times < 0) {
times = 0;
}
int[] all = new int[maxNum];
for (int i = 0; i < all.length; i++) {
all[i] = i;
}
/* https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle */
int[] indices = new int[Math.min(maxNum, times)];
for (int i = 0, j, value; i < indices.length; i++) {
j = intRangeRandom(i, all.length - 1);
value = all[j];
all[j] = all[i];
indices[i] = all[i] = value;
}
return indices;
}
}
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