how can I add a java api to my drupal 7 site? I have a java drivers and java api (also .NET and C# and Unity3d) from an SDK that I need to integrate into my Drupal 7 site eg as a plug in. Can I create a module with a java api? (or if not, then from the C# .net, or United3d?)
Drupal is a php framework, you can't create a java module inside drupal. There are solutions like this that lets you point to a external java application. The other option is to communicate with the other (Java/C#/Whatever) applications with web services like REST or SOAP (or a simple XML file).