JCRandom.java

package ee.esutoniagodesu.util;

import java.util.*;

/**
 * class for creating random variables of any kind
 */
public final class JCRandom {

    /**
     * generates random integet value
     *
     * @param start start
     * @param end   end
     * @return value between start and end
     */
    public static int between(int start, int end) {
        int result;
        end += 1;

        if (end > start) {
            Random rand = new Random();
            int interval = Math.abs(end - start);
            result = start + rand.nextInt(interval);
        } else if (end == start) {
            result = start;
        } else {
            throw new IllegalArgumentException();
        }

        return result;
    }

    /**
     * @param seed seed
     * @return value between 0 and seed
     */
    public static int integer(int seed) {
        Random rand = new Random();
        return rand.nextInt(seed);
    }

    /**
     * generates double matrix with randomly initiated relations.
     *
     * @param ydim  - y dimension
     * @param xdim  - x dimension
     * @param count - how many relations
     * @param value - relation value
     * @return double matrix
     */
    public static double[][] getMatrix(int ydim, int xdim, int count,
                                       double value) {
        double[][] result = new double[ydim][xdim];

        List<Integer> keys = new ArrayList<>();
        int n = ydim * xdim;
        for (int i = 0; i < n; i++) {
            keys.add(i);
        }

        Collections.shuffle(keys);

        int pos, y, x;

        for (int i = 0; i < count; i++) {
            pos = keys.get(i);
            x = pos % xdim;
            y = (pos - x) / xdim;
            result[y][x] = value;
        }

        return result;
    }

    public static String random13B() {
        return Long.toString(UUID.randomUUID().getMostSignificantBits(), Character.MAX_RADIX);
    }
}