subList is a view, and touching the parent invalidates it

List.subList does not copy. It returns a window onto the original, and any structural change to the parent makes every method on that window throw - which turns a caching or pagination helper into a landmine.

• Utilities: a private constructor with only static members documents a utility class
• Utilities: new Random(seed) produces the same sequence every run
• Utilities: UUID.nameUUIDFromBytes produces the same UUID for the same input
• Utilities: Base64 encodes bytes into ASCII text and decodes them back
• Utilities: HexFormat converts bytes to and from a hex string
• Utilities: Arrays.deepEquals compares nested arrays, equals does not

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Published 2026-08-25

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