Factorial with double vs BigInteger

import java.math.BigInteger;
import java.text.DecimalFormat;
import java.text.NumberFormat;

public class FactorialTest {

    private static final NumberFormat formatter = new DecimalFormat("#");

    public static void main(String[] args) {
        double fact = 1;
        BigInteger bigFact = new BigInteger("1");
        int i = 0;
        do {
            i++;

            fact *= i;
            bigFact = bigFact.multiply(new BigInteger(String.valueOf(i)));

            final String bigFormat = bigFact.toString();
            System.out.println(i + " = " + bigFormat);

            final String doubleFormat = formatter.format(fact);
            if (!doubleFormat.equals(bigFormat)) {
                System.out.println("  != " + doubleFormat);
            }

        } while (i < 100);
    }

}