immutable-args
Cleaner, more functional implementation of Robert C Martin's Args program in Clean Code, page 194. This repository is not an endorsement of Robert C Martin's books or views. I found his example to be far too verbose and non-functional for my liking, so I figured I'd rewrite it using Java 8.
Optional
Instead of throwing exceptions for missing values, I've opted for returning Optional results, so the client may decide to handle missing values in a more graceful manner.
Immutable
I wanted to make it 100% immutable, but with as few dependencies as possible. Unfortunately there are no default ImmutableMaps in Java, so ArgsImmutable uses a HashMap under the hood. Once constructed however, Args is entirely read-only.
Zero nulls
Unlike the original example, immutable-args does not use null at all - any NullPointerExceptions therefore are entirely the fault of anybody using it. This makes debugging that little bit easier.