As you can see from my question(How to use Java Documentation ??) , I am a java learner. I really want to know that how i can use the java documentation. Is it really helpful ? If yes, in what sense is it helpful .. Any help will be appreciated
I suppose you are talking about Java API documentation. In the same way you can create API documentation for your own code, as Balasubramanian mentioned, Java API has its own documentation.
This documentation (also known as javadoc) contains information about all the classes made available by a standard JVM and how to use it. So, you don't have to code everything by yourself but rather use these utility and foundation classes.
You can try googling by "javadoc" and find more info about it.