web3j

Web3j is a Java library for interacting with the Ethereum blockchain. It is designed to make it easy for Java developers to build applications that interact with the Ethereum blockchain and smart contracts.

Web3j is open source and available for use under the MIT license. It can be installed using a build tool like Maven, and can be used in both standalone Java applications and Android apps. Web3j is a widely used library in the Ethereum development community and is well-documented, making it a good choice.