Iván said:
Do you mean the features of the classes? download and install the
documentation of Java and take a look to the API reference
Yes. Download the Java API documentation. It is a ready reference for
Core Java classes. You cannot read like a book and learn.
To learn about the basic Java classes, you also need a good Java book.
I suppose you already have one. Start with a beginner level book or
tutorial, so that you do not get overwhelmed. (I initially got
overwhelmed when I picked up a Java book for intermediate to advanced
users, instead of a beginner level book)