package rebelsky.exam1;

import java.math.BigInteger;

/**
 * Something that counts the number of times a method is
 * called.
 */
public class Fib
{
  /** A count of the number of times the method is called. */
  static long calls;

  /** Get the number of times the method is called. */
  public static long getCalls()
  {
    return calls;
  }

  /** Reset the count to 0. */
  public static void reset()
  {
    calls = 0;
  }

  /** 
   * Compute the nth Fibonacci number. The Fibonacci numbers
   * are given by the rules
   *  * The 0th Fibonacci number is 1
   *  * The 1st Fibonacci number is 1
   *  * The nth Fibonacci numbers is the sum of 
   *    the n-1st Fibonacci number and the n-2nd Fibonacci number
   * That is, the sequence
   *   1, 1, 2, 3, 5, 8, 13, 21, ....
   */
  public static BigInteger fib(int n)
  {
    calls = calls+1;
    if (n < 2) {
      return BigInteger.ONE;
    }
    else {
      return fib(n-1).add(fib(n-2));
    }
  }

} // class Fib