Yup. Minecraft is coded in JAVA.
The original (or Java Edition) version of Minecraft was written using the Java programming language and the Lightweight Java Gaming Library (LWJGL). Minecraft was originally written in Java, but it is now a dual Java/C++ project because of better performance, IMO.
Though, I think Minecraft's pocket Edition was written using the C++ programming language since Java was not supported by iOS (the operating system developed by Apple for the iPhone and iPad).
Java had some problem, as it was difficult to do certain kinds of optimizations, which meant that the game always had difficulty running well on older machines. When the “Pocket Edition” of Minecraft was written, they actually started over and rewrote the whole game in C++. This edition was much more efficient, and stresses the hardware less, which makes it possible for it to run on low-powered devices. Unfortunately, because they had to redo everything from scratch, it was usually behind the regular edition on features.
The “Windows Edition” of Minecraft was a concerted effort to catch the C++ version up to the Java version, which has now generally succeeded. It’s still a separate codebase, though, and they aren’t entirely compatible with each other (this is reflected by the multiplayer situation—the Java and the C++ editions both support multiplayer, but only with players using the same edition.
There was one major downside to the C++ Minecraft: because C++ is a fully compiled language, it was more difficult to make mods for it. Java programs are relatively easy to reverse engineer, so the mods can be very sophisticated, but practically speaking, C++ is only moddable in the areas where the programmers designed it to be moddable.