Using BigInteger in Java to calculate unsigned long value

I need to convert this C# code to Java where __count is a ULong type and STR_LENGTH=8. How do I use BigInteger here.

        static test()
        {
            int index;
            // compute ( 10 ^ STR_LENGTH ) - 1

            __count= 1UL;
            for (index = 0; index < STR_LENGTH; ++index)
            {
                __count*= 10UL;
            }
            __count--;
        }