Java is powerful object orient programming language. Its usage is very wide in the software industry. It is used for enterprise applications development. In Big Data also it is used widely to develop and run the applications for Big Data.
Java come in three versions
Java Standard Edition:
The Java Standard Edition is used for making program for desktop gui and console based business or utility applications.
Java Enterprise Edition:
This is also know as Java EE which is widely used for enterprise web applications of irrespective of size.
There is another version which is actually an Operating system The Andoid. Here also Java is used for developing mobile applications for Android phones.
So, If you want make your career in any of the filed or interested in these technologies then you should learn Java Programming Language.