Complete Program

When fib(n) is computed recursively, very many activations are created and destroyed. Sometimes the time it takes to compute fib(n) is used as a benchmark, a program that tests the speed of a computer. Here is a bare-minimum program for fib(n):

class FibonacciCalc
{
  public int fib( int n )
  {
    if ( n == 1 ) 
      return 1;
    else if ( n == 2 ) 
      return 1;
    else
      return fib( n-1 ) + fib( n-2 );
  }
}

class FibonacciTester
{
  public static void main ( String[] args)
  {
    int argument = Integer.parseInt( args[0] );  // Get N from the command line.
    
    FibonacciCalc f = new FibonacciCalc();
    int result = f.fib( argument );
    System.out.println("fib(" + argument + ") is " + result );
  }
}

Run the program with an argument on the command line, like java FibonacciTester 20 Here are some results of running the program on my IBM ThinkPad 380ED. You might wish to run the program on your computer and compare speeds.

It takes a few seconds for the Java system to load and start running. This time is included in these measurements.