public BigInteger shiftLeft(int n)
private int[] shiftLeft(int[] mag, int n)
    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));    }