This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Indeed, this is on of the most popular questions in mailing lists.
Currently you can not run a unique SonarQube analysis for multiple languages but you can run different analysis for each language used.
There are several plugins for the most well-known languages that include hundreds of coding rules and definitely it worth the effort to analyze a project for all languages and improve the quality.