I assume you know this by now but, just in case, Android Studio has built-in support for two languages, Java and Kotlin, which I think of as a streamlined (more concise) Java. Android Studio also allows the use of other languages like C++ but I'm not sure what limitations and rules govern that.
In short, Java is already there in Android Studio and you can start writing Java code there as soon as have Android Studio installed without having to install anything else.