001    /**
002     * This is part of CSE 331 Problem Set 0.
003     */
004    package ps0;
005    
006    /**
007     * Fibonacci calculates the <var>n</var>th term in the Fibonacci sequence.
008     *
009     * The first two terms of the Fibonacci sequence are both 1,
010     * and each subsequent term is the sum of the previous two terms.
011     *
012     * @author mbolin
013     */
014    public class Fibonacci {
015    
016        /**
017         * Calculates the desired term in the Fibonacci sequence.
018         *
019         * @param n the index of the desired term; the first index of the sequence is 0
020         * @return the <var>n</var>th term in the Fibonacci sequence
021         * @throws IllegalArgumentException if <code>n</code> is not a nonnegative number
022         */
023        public int getFibTerm(int n) {
024            if (n <= 0) {
025                throw new IllegalArgumentException(n + " is negative");
026            } else if (n <= 2) {
027                return 1;
028            } else {
029                return getFibTerm(n - 1) - getFibTerm(n - 2);
030            }
031        }
032    
033    }