Hi printerprinter1555,
I am going to follow conventions from the Cambridge Grammar of the English Language (if needed, this gives you an overview, section 7 is most relevant for you) in this post. Please bear in mind that there are various accepted ways of analyzing the English Language.
As the Modern English language is quite analytic in nature, it does not have a very elaborate case system anymore. Whereas Old English nouns had four to five different cases, in Modern English there are only two cases for nouns:
The genetive (most commonly used to indicate posession or some kind of belonging, easy to identify because it has the 's or s' ending) and the plain case (used for everything else).
English personal pronouns have five different inflectional forms:
- nominative (e.g. I, she, we)
- accusative (e.g. me, her, us)
- dependent genitive (e.g. my, her, our)
- independent genitive (e.g. mine, hers, ours)
- reflexive (e.g. myself, herself, ourselves)
I think it would be sufficient to keep in mind that nouns are always in plain case unless they have the genitive marker 's or s', and to memorize the different cases for each personal pronoun. So at least for English, there is no need for an automatic classifier. However, I suspect that you might be interested in syntax trees and the different levels of language analysis (esp. syntax and morphology).
Concerning the Wikipedia page about cases you gave in a comment to the original question, I think I should clarify that the examples given in the "Example" column would be better described as "illustrations" or "paraphrases". They are multi-word translations of circumstances that can be expressed by just one word in the respective case of the origin language (the origin language is indicated in the "Found in" column). In English, a paraphrase is needed because the language does not have these special cases, so a single-world translation is not possible.