# Computing Fibonacci numbers

Computing Fibonacci numbers

import java.io.*;
import java.math.BigInteger;

/**
* BigFib is a simple class for computing Fibonacci
* numbers, using the Java multi-precision integer
* class java.math.BigInteger.
*/
public class BigFib {
BigInteger last;
BigInteger next;
int n;

/**
* Create a new BigFib object, initialized to 0 on
* the Fibonnacci sequence.
*/
public BigFib () {
n = 0;
last = new BigInteger("0");
next = new BigInteger("1");
}

/**
* Compute c more Fibonnacci numbers, returning the
* last one. Ideally, c should be even and >0.
* If you want to print the numbers too, pass printTo
* as non-null.
*/
public BigInteger getFib(int c, PrintStream printTo) {
BigInteger tmp;
for( ; c > 0; c -= 2) {
if (printTo != null) printTo.println(" " + n + "\t" + last);
if (printTo != null) printTo.println(" " + n + "\t" + next);
}
if (c == 0) return next;
else return last;
}

/**
* Default limit for self-test.
*/
public static final int defaultLimit = 100;

/**
* Self-test code, accepts an integer from the
* command line, or uses the default limit.
*/
public static void main(String args[]) {

BigFib fib = new BigFib();

System.out.println("\t\t Fibonacci sequence!");
System.out.println("");

System.out.println();
int limit = 100;
if (args.length > 0) {
try { limit = Integer.parseInt(args[0]); }
catch (NumberFormatException nfe) {
System.err.println("Bad number, using default " + limit);
}
if (limit < 1) {
limit = defaultLimit;
System.err.println("Limit too low, using default " + limit);
}
}