MathUtils.java

package utils;

import java.util.HashSet;
import java.util.Random;
import java.util.Set;

public class MathUtils {

	private static Random random = new Random();

	/**
	 * 
	 * @param startidx
	 * @param endidxIncl 
	 * @param k how many random numbers.
	 * @return set of unique random numbers (in a set because, anyways, 
	 * the order doesn't matter and the func. is non-deterministic)
	 */
	public static Set<Integer> randUniq(int startidx, int endidxIncl, int k) {
		Set<Integer> r = new HashSet<>();
		while(r.size()!=k) {
			int i = random.nextInt(endidxIncl + 1);
			if(i>=startidx && i<=endidxIncl) {
				r.add(i);
			}
		}
		return r;
	}
}