BitcoinJ
bitcoinj is a library for working with the Bitcoin protocol. It can maintain a wallet, send/receive transactions without needing a local copy of Bitcoin Core and has many other advanced features. It’s implemented in Java but can be used from any JVM compatible language: examples in Python and JavaScript are included.

Web3j
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.

The Java and the Blockchain talk provides an overview of blockchain, Ethereum and web3j.
Fabric
Fabric is a high level Python (2.7, 3.4+) library designed to execute shell commands remotely over SSH, yielding useful Python objects in return:
Linux
It builds on top of Invoke (subprocess command execution and command-line features) and Paramiko (SSH protocol implementation), extending their APIs to complement one another and provide additional functionality.
Note
Fabric users may also be interested in two strictly optional libraries which implement best-practice user-level code: Invocations (Invoke-only, locally-focused CLI tasks) and Patchwork (remote-friendly, typically shell-command-focused, utility functions).
FISCO
FISCO bcos is a safe and controllable enterprise level financial alliance chain underlying platform developed by domestic enterprises and opened to the outside world. It was built in collaboration with the open source working group of golden chain alliance and officially opened to the outside world in 2017. As of May 2020, the community has gathered more than 1000 enterprises and institutions and more than 10000 community members to participate in co construction and co governance, and has developed into the largest and most active domestic open source alliance chain ecosystem. The availability of the underlying platform has been tested by extensive application practice. Hundreds of application projects have been developed based on FISCO bcos underlying platform, and more than 80 have been running stably in the production environment, covering cultural copyright, judicial services, government services, Internet of things, finance, smart community and other fields.