Welcome back to the third part of my rolling blog on building CLIAR, a lightweight, transparent command‑line argument parser for Java. In Part 2 , we added support for short options, long options, and key–value pairs. This chapter focuses on two major improvements: separating concerns inside the parser introducing a formal option‑registration system so CLIAR can validate user input This is the point where CLIAR becomes a real utility rather than a loose collection of parsing rules. You can find current snapshots of the code on my GitHub page. Defining rules for option names Before we can validate user input, we need clear rules for declared option names — the names the developer defines in code. To keep CLIAR predictable and easy to read: Short option names must be single alphabetic characters. Long option names must start with a letter and may contain letters, digits, or hyphens. Values and positional arguments remain unrestricted.…