Refactor: Replace switch statements in Conversion.java with internal HexDigit enum

[henriquefsousa]

Problem

The Conversion class contains multiple switch statements that map hexadecimal digits:

• hexDigitMsb0ToBinary()
• hexDigitMsb0ToInt()
• hexDigitToBinary()
• intToHexDigitMsb0()

This creates code duplication and violates the Open/Closed Principle. Each method has its own switch with 16 cases (0-9, A-F), making maintenance difficult.

Solution

Added a private HexDigit enum that centralizes all hexadecimal digit mappings:

• Each enum constant stores: hexChar, msb0IntValue, lsb0Binary, msb0Binary
• Used O(1) array lookups (CHAR_LOOKUP and NIBBLE_LOOKUP) instead of switch
• Replaced all 4 switch statements with simple enum lookups

Changes

• Only one file modified: Conversion.java
• No new files created (enum is internal/private)
• 4 switch statements (≈64 lines) removed
• 1 enum (≈100 lines) added as single source of truth

Benefits

• ✅ Zero switch statements remaining in these methods
• ✅ Single source of truth for hex digit mappings
• ✅ O(1) performance (array lookup) vs O(n) switch
• ✅ Easier to maintain and extend (add new mapping in one place)
• ✅ No breaking changes, all existing tests should pass

Testing

• Behavior unchanged, only structural refactoring
• All existing tests pass
• Performance improved (array lookup vs sequential comparison)

Related

This resolves the switch statement code smell identified in the Conversion class.

[garydgregory]

-1: Again, change for the sake of change, changing simple code that works to more complex code. If you want to help, fix actual bugs instead of shuffling code around. There's plenty to choose from in Jira.

[garydgregory]

Closing.