import java.util.Random;

/** A class used to create pseudorandom numbers */
public class RandomGen extends Object implements RandomInterface
{
   private Random r;

  /** Create a new random number generator based on the current time.
   */
   public RandomGen()
   { // initializes r based on the current time
      r = new Random();
   }

  /** Create a new random number generator using <TT>seed</TT> as a seed.
   * A seed is a number used to generate a certain pattern of random
   * numbers.  It is <B>NOT</B> the upper or lower bound, nor the expected
   * value.
   * @param seed the seed for the random number generator
   */
   public RandomGen(long seed)
   {  r = new java.util.Random(seed);
   }

  /** Select a number from an exponential distribution.
   * @param returns random number selected from exponential distribution
   *   with expected value alpha.
   * @return a random real number
   */
   public double nextExp (double alpha)
   {  double x;
      while ((x = r.nextDouble()) == 0); //loop until x!=0
      return (- alpha * Math.log(x));
   }

  /** Select a number from a uniform distribution.
   * @post returns a random int uniformly distributed between low and
   *   high inclusive.
   * @param low the minimum random integer to return
   * @param high the maximum random integer to return
   * @return a random integer between low and high
   */
   public int nextUniformInt (int low, int high)
   {  double x;
      while ((x = r.nextDouble()) == 1); //loop until x!=1;
      return (int) Math.floor(x * (high - low + 1) + low);
   }
}