Not a Java implementation, but the original game was written in Java. Later, Microsoft bought Minecraft and rewrote it (Bedrock edition) which runs on Xbox, tablets, etc. But, the community writes mods in Java.

Now both exist and get roughly the same feature set now, but the Java version remains popular given the vast variety of mods and servers.

It’s the Java version of the game, not a game version of Java.

There’s a native version called bedrock