Which languages are used to develop google..??

Answer 1

They are currently switching to the Go language.

Answer 2

There is no single programming language.  Google has a very open development environment with many different service APIs.  

Java, Javascript, C++, Python, Go, Sawzal (a custom logging language), and probably a few other languages are supported. 

Search is mostly based on C++ and some Python. 

Ads is a Java/SQL stack.

Google Apps is a Javascript/Java/C++ stack.