src/main/java/org/xmlet/xsdparser/xsdelements/AttributeValidations.java
static Integer validateNonNegativeInteger(String elementName, String attributeName, String value){
        try {
            int intValue = Integer.parseInt(value);

            if (intValue < 0){
                throw new ParsingException("The " + elementName + " " + attributeName + " attribute should be a non negative integer. (greater or equal than 0)");
            }

            return intValue;
        } catch (NumberFormatException e){
            throw new ParsingException("The " + elementName + " " + attributeName + "  attribute should be a non negative integer.");
        }
    }
static Integer validateNonNegativeInteger(String elementName, String attributeName, String value){
        try {
            int intValue = Integer.parseInt(value);

            if (intValue < 0){
                throw new ParsingException("The " + elementName + " " + attributeName + " attribute should be a non negative integer. (greater or equal than 0)");
            }

            return intValue;
        } catch (NumberFormatException e){
            throw new ParsingException("The " + elementName + " " + attributeName + "  attribute should be a non negative integer.");
        }
    }
Validates if a given String is a non negative {@link Integer}. Throws an exception if the {@link String} isn't a non
negative {@link Integer}.
@param elementName The element name containing the field with the {@link Integer} value.
@param attributeName The name of the attribute with the {@link Integer}.
@param value The value to be parsed to a {@link Integer} object.
@return The parsed {@link Integer} value.