CashDispenser

public class CashDispenser
{
    private final static int INITIAL_COUNT = 500;
    private int count;
    public CashDispenser()
    {
        count = INITIAL_COUNT;
    }

    public void dispenseCash(int amount)
    {
        int billRequired = amount / 20;
        count -= billRequired;
    }

    public boolean isSufficientCashAvailable(int amount)
    {
        int billRequired = amount / 20;

        if(count >= billRequired) return true;
        else  return false;
    }
}