What are the methods to call on a string and what kind of class it is object of?

Answer 1

I am not pretty sure what you want to ask. The String is Java build in class. When you type String s = new String(); you are instantiating a new object of class String. String as a built-in class has many built-in methods you can use. The best way to check what you can use and how is to check Java documentation:

https://docs.oracle.com/javase/8/docs/api/java/lang/String.html

Answer 2

im not sure if i understand your question right, but here is a list of nearliy all string methods
https://docs.oracle.com/javase/7/docs/api/java/lang/String.html