I download the Java JDK 6 source code .tar file, and I extracted all the files from it using java command. And I get those control, deploy, hotspot, j2se, etc. What do I do now to actually see all the source code? Any solutions of using Eclipse to do that?
If you've got eclipse configured correctly, you should just be able to hit F3
on (or otherwise search for) a type like java.lang.Object
and be taken directly to its source. If not, you'll get a screen with a big "Attach Source" button, which you can use to point eclipse at the .zip file you downloaded.
You seem to be asking about setting up an eclipse project for the Java source code. There's no need to do that unless you plan on modifying the code.
If you are using eclipse and setup your project to use the a JDK installed on your machine you do no need to download the source as its included with jdk by default. Eclipse will recognize that you are using a jdk and you can "Open Declaration" on any object that is part of the standard library.