Java isbasically a programming language and computing platform first released by Sun Microsystems in 1995. There are lots of applications and websites that will not work unless you have Java installed, and more are created every day. Java is fast, secure, and reliable. From laptops to datacenters, game consoles to scientific supercomputers, cell phones to the Internet, Java is everywhere!
  java is a object oriented  programming language.Using this we would create any apps like android,banking application and etc.its very secure one. everything based on class.
   security related application might be created by have more flixblity like platform indepentance and open source .that's created by sun micro system owened by oracle
   java have j2we,j2me and etc
        j2me is used for mobile application.