In https://docs.web3j.io/4.8.7/quickstart/#maven-plugin, do references to version `4.8.1` of `web3j-maven-plugin` but this version does not exist in mvnrepository (https://mvnrepository.com/artifact/org.web3j/web3j-maven-plugin) neither releases page of own project: https://github.com/web3j/web3j-maven-plugin/releases. The correct version is `4.8.2`, present in mvnrepository and release page.