Web3j is a highly modular, reactive, type safe Java and Android library for working with Smart Contracts and integrating with clients (nodes) on the Ethereum network. This allows you to work with the Ethereum blockchain, without the additional overhead of having to write your own integration code for the platform
Hyperledger Besu is an Ethereum client designed to be enterprise-friendly for both public and private permissioned network use cases, with an extractable EVM implementation.