How to get know of many functions in java?

Answer 1

Practice

Answer 2

Well, first you should code many kinds of codes for knowing all the data types.
Second I think every IDE has this feature that when you use a data type and add . so either you'll wait and get a list of functions and more or press on Ctrl + Alt and get this list.

Answer 3

Practice make perfect.

If you use intense the java Documentation and when you search for example code for you problem in the web.
You only become perfect when you make intnsive use of all possibilities.
Coding is like to learn a language for example you like to learn German. Do you need Practice, Practice and Practice...

Some links:
https://doc.oracle.com/javase/10/docs/api/index.html

https://hackerrank.com

This Page sololearn

And many more ...

Regards kiuziu