im familiar with java api, but some of you told me that it is in the api all the methods that i want to know, but how to understand or analyze how to use the methods in the java api? i know what it does because it is there written, but when will i apply that? or how?
IMO, you need to understand the concepts of the Java Class Heirarchy and Inheritance. Once you understand that, you will be much better equipped to use the API.