I saw java is very popular language so I want know lot of information about java

Errr Google?

Best place to start as it's a massive field.

First thing to do is figure out what you need/want to do with Java. With this in mind it's a lot easier to look for answers.

Try: Java Technology (http://java.sun.com)
Also take a look at the java books at: oreilly.com -- Welcome to O'Reilly Media, Inc. (http://www.oreilly.com/)