Java
C++ and
Java are the main languages for production. Search is mostly written in C++, while a lot of the ads infrastructure is written in
Java. Python is used as glue, for things like development tools and administration tools. There's a lot of other random languages here and there though - there are projects that use everything from Haskell to perl.
google also has some of their own languages that exist only within google, such as sawzall.
