Is there any way I can learn in more details?

Question

I new in Java community.. I have finished course here.. but I need some concepts like where to use HashMap, where to create class, what else I can find in packages like java.util.Scanner and how to use other methods??

Can anyone kindly share some free web links or book links where I can learn in details..

Answer 1

All classes that are standard in Java are completely documented officially by Oracle.
For example, check this document on Java 8's java.util.HashMap:
https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html
java.util.Scanner is documented at:
https://docs.oracle.com/javase/8/docs/api/java/util/Scanner.html

HashMap is great when you need a hash table or container for key-value pairs. HashSet is great for situations where you just need to store sets of distinct values and don't care about keys. HashMap is Java's analogue to Python's dict.

Whenever programming in any language including Java, it is good to look for existing standard classes, packages, and then libraries to do what you want before writing the code yourself. In cases where the problem can be solved trivially by your own code, just don't search very hard before doing it yourself. With experience, you'll remember if there is an existing solution or not. If you need third party code, Java's way to do that is jar files.

One example of using third party code is parsing JSON. I'm not sure why Java has no standard JSON parser yet but the best way seems to still be a library like this:
http://www.java2s.com/Code/Jar/j/Downloadjsonsimple11jar.htm

Answer 2

Thanks a lot Josh.. ❤