Modernize Java Code

Update the target code to use modern Java features:

• Records instead of mutable POJOs where the type is a value carrier
• Switch expressions with arrow syntax and exhaustiveness checking
• Pattern matching for instanceof and switch
• Local variable type inference (var) where it helps readability
• Virtual threads (Java 21+) for I/O-bound operations — Executors.newVirtualThreadPerTaskExecutor()
• Sealed classes when the type hierarchy is closed
• Text blocks for multiline strings
• Sequenced collections (Java 21+) where ordered access matters
• Collection factory methods (List.of, Map.of, Map.entry)

Constraints