CustomField names need Type prefix and CamelCase

ruleset.xml

<?xml version="1.0" encoding="UTF-8"?>
<ruleset xmlns="http://pmd.sourceforge.net/ruleset/2.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" name="Default ruleset used by the CodeClimate Engine for Salesforce.com Apex" xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 https://pmd.sourceforge.io/ruleset_2_0_0.xsd">
   <description>Default ruleset</description>

    <rule name="CustomFieldNamingConvention" language="xml" message="Incorrectly named field" class="net.sourceforge.pmd.lang.rule.XPathRule">
        <properties>
            <property name="version" value="2.0"/>
            <property name="xpath">
                <value><![CDATA[
                //CustomField[
                    (fullName/text[not(matches(@Image, "chk_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Checkbox"]) or
                    (fullName/text[not(matches(@Image, "txt_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Text"]) or
                    (fullName/text[not(matches(@Image, "txa_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Textarea"]) or
                    (fullName/text[not(matches(@Image, "txr_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Richtext"]) or
                    (fullName/text[not(matches(@Image, "txl_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="LongTextArea"]) or
                    (fullName/text[not(matches(@Image, "num_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Number"]) or
                    (fullName/text[not(matches(@Image, "dat_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Date"]) or
                    (fullName/text[not(matches(@Image, "lkp_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Lookup"]) or
                    (fullName/text[not(matches(@Image, "mdr_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="MasterDetail"]) or
                    (fullName/text[not(matches(@Image, "dtm_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="DateTime"]) or
                    (fullName/text[not(matches(@Image, "url_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Url"]) or
                    (fullName/text[not(matches(@Image, "pkl_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Picklist"]) or
                    (fullName/text[not(matches(@Image, "pkm_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="MultiselectPicklist"]) or
                    (fullName/text[not(matches(@Image, "cur_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Currency"]) or
                    (fullName/text[not(matches(@Image, "pct_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Percent"]) or
                    (fullName/text[not(matches(@Image, "fcur_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Currency"] and formula) or
                    (fullName/text[not(matches(@Image, "rcnt_([A-Z][a-z0-9]+)+__c"))] and type/text[@Image="Summary"] and summaryOperation/text[@Image="count"]) 
                ]
                ]]></value>
            </property>
        </properties>
    </rule>
</ruleset>