Get fibonacci number of given nth term.

Fibonacci.java

import java.math.BigInteger;

public class Fibonacci {

    public static void main(final String... args) {
        final int n = Integer.parseInt(args[0]);
        if (n < 0) {
            throw new IllegalArgumentException("n(" + n + ") is negative");
        }
        if (n == 0) {
            System.out.println(0);
            return;
        }
        if (n == 1) {
            System.out.println(1);
            return;
        }
        final BigInteger[] a = new BigInteger[]{BigInteger.ZERO, BigInteger.ONE};
        BigInteger o;
        for (int i = 2; i <= n; i++) {
            o = a[0];
            a[0] = a[1];
            a[1] = a[1].add(o);
        }
        System.out.println(a[1].toString());
    }
}