Fibonacci calculator - O(logN)

Calculator.java

/*******************************************************
Program Number: A1_1
Purpose/Description: <a brief description of the program>
Author: Alastair Paragas
Due date: 09/09/2015
Certification:
I hereby certify that this work is my own and none of it is the work of
any other person.
    Alastair Paragas
*******************************************************/

package assignment1.problem1;

public class Calculator {
    
    /**
     * Helper for calculating the nth Fibonacci number
     * @param n - Term # in the Fibonacci sequence.
     * @return Array where element 0 is the nth Fibonacci number and element 1
     *  is the nth - 1 Fibonacci number
     */
    private int[] fibHelper(int n) {
        
        if (n == 0) {
            return new int[]{0,0};
        } else if (n == 1) {
            return new int[]{1,0};
        }
        
        // Odd Term (at least, Term #3) - use old strategy of adding 2 
        // previous terms
        if (n % 2 == 1) {
            
            int[] fibNthTuple = fibHelper(n - 1);
            int fibNthTerm = fibNthTuple[0];
            int fibNthMinus1Term = fibNthTuple[1];
            
            return new int[]{fibNthTerm + fibNthMinus1Term, fibNthTerm};
            
        }
        
        // Even Term (at least, Term #2): F(2n) = (F(n))^2 + 2(F(n) * F(n-1))
        int[] fibNthTuple = fibHelper(n/2);
        int fibNthTerm = fibNthTuple[0];
        int fibNthMinus1Term = fibNthTuple[1];
        
        return new int[]{fibNthTerm * fibNthTerm + 2 * fibNthTerm * 
                fibNthMinus1Term, fibNthTerm * fibNthTerm + fibNthMinus1Term * 
                fibNthMinus1Term};
        
    }
    
    /**
     * Calculates the nth Fibonacci number
     * @param n - Term # in the Fibonacci sequence
     * @return Fibonacci number
     */
    public int fib(int n) {
        
        // 0th Term is 0, 1st Term is 1
        if (n < 2) {
            return n;
        }
        
        
        return fibHelper(n)[0];
        
    }
    
}