public BigInteger getBigInteger(String attrName) {
        BigDecimal bd = getNumber(attrName);
        return bd == null ? null : bd.toBigInteger();
    }
public BigInteger getBigInteger ( String attrName ) { BigDecimal bd = getNumber ( attrName ) ; return bd == null ? null : bd . toBigInteger ( ) ; }
Returns the value of the specified attribute in the current item as an
<code>BigInteger</code>; or null if the attribute doesn't exist.

@see #isNull(String) #isNull(String) to check if the attribute value is
null.
@see #isPresent(String) #isPresent(String) to check if the attribute
value is present.

@throws NumberFormatException
if the attribute value is null or not a valid representation
of a {@code BigDecimal}.