IDMask is a Java library for masking internal ids (e.g. from your DB) when they need to be published to hide their actual value and to prevent forging. It has support optional randomisation has a wide support for various Java types including long, UUID and BigInteger.
Bytes is a utility library that makes it easy to create, parse, transform, validate and convert byte arrays in Java. It supports endianness as well as immutability and mutability, so the caller may decide to favor performance.