if (sign == 0 || magnitude.length == 0)
int nInts = n >>> 5; int nBits = n & 0x1f; int magLen = mag.length; int newMag[] = null;  if (nBits == 0)
    public BigInteger shiftLeft(int n)    {        if (sign == 0 || magnitude.length == 0)        {            return ZERO;        }        if (n == 0)        {            return this;        }        if (n < 0)        {            return shiftRight( -n);        }        return new BigInteger(sign, shiftLeft(magnitude, n));    }