BigInteger: strange problem

[Randall Twede]

i finally found a formula for solving euler116. it worked fine using longs and a smaller input but i had to change to BigInteger. the result is strange. i have these lines of code
BigInteger count = BigInteger.ZERO;

BigInteger quotient = num.divide(den);
System.out.println(quotient);
count.add(quotient);
System.out.println(count);

it prints out (for example)
9
0

how is this possible???
if quotient is 9 and count starts out being 0 it should print out 9!!!
i can post entire code if necessary

[Randall Twede]

here is entire code

import java.math.BigInteger;

class Euler119  implements Problem
{
	final int spaces = 10;
	BigInteger count = BigInteger.ZERO;

	public String solve()
	{
		ways(2);
		BigInteger answer = count;
		//ways(3);
		//answer.add(BigInteger.valueOf(count));
		//ways(3);
		//answer.add(BigInteger.valueOf(count));
		return answer.toString();
	}
	//b = 50-(L*c)
	//(c+b)! / c!b!
	private void ways(int size)
	{
		for( int tiles = 1; tiles <= spaces / size; tiles++)
		{
		BigInteger num = factorial(tiles + (spaces - size * tiles));
		System.out.println(num);
		BigInteger den = factorial(tiles).multiply(factorial(spaces - size * tiles));
		System.out.println(den);
		BigInteger quotient = num.divide(den);
		System.out.println(quotient);
		count.add(quotient);
		System.out.println(count);
		}
	}
	
	private BigInteger factorial(long number)
	{		
		BigInteger answer = BigInteger.ONE;
		for(long i = 1; i <= number; i++)
		{
			BigInteger next = BigInteger.valueOf(i);
			answer = answer.multiply(next);
		}
		return answer;
	}
	
	public String getMessage()
	{
		return "test";
	}
}

it prints out
362880
40320
9
0
40320
1440
28
0
5040
144
35
0
720
48
15
0
120
120
1
0

[Randall Twede]

never mind. this is the second time i made this mistake.
should be count = count.add(quotient);