Java is a high-level programming language originally developed by Sun Microsystems and released in 1995. But it is owned by Oracle now. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX.
It is used for:
Mobile applications (specially Android apps)
Web servers and application servers
And much, much more!
Why to Learn java Programming?
It has a huge community support (tens of millions of developers)