I have a Java Class that I suspect can use a ReflectionUtil here because there are too many switch/cases, any advice?
The only problem I see with this code is, that for extending the enum, you need to change two methods in the code, which spreads out changes instead of keeping them local to a single place.
You could however harness the power of the java enum (which can have fields and methods) to make the changes locally.
Something along the lines of:
enum ParserClassType {
    SPECIFIC_XML(SpecificXMLParser.FILE_TYPE_OUTPUT) {
        public ParserClass createParser(InputStream is, etc, ...) {
            return new SpecificXMLParser(...);
        }
    },
    XML(GenericXMLParser.FILE_TYPE_OUTPUT) {
        public ParserClass createParser(InputStream is, etc, ...) {
            return new GenericXMLParser(...);
        }
    },
    ...

    private final String fileExtension;

    private ParserClassType(String fileExtension) {
        this.fileExtension = fileExtension;
    }

    public String getFileExtension() {
        return fileExtension;
    }

    public abstract ParserClass createParser(InputStream is, etc, ...);
}

public static String getFileExtension(...) {
    ParserClassType parserClassType = ...
    return parserClassType.getFileExtension();
}

public ParserClass getParserClass(...) {
    ParserClassType parserClassType =  ...
    return parserClassType.createParser(...);
}

As you see, when you add a new type, you simply have to extend the enum. All the client code stays unmodified.
Apart from that, please look up the java naming conventions. Variables should start with lower case letters and definitely not shadow their class names.
Furthermore, getParserClass() / ParserClass is badly named, as it clearly involves around a concrete parser / parserInstance, not around a class.