How to Define Method to Take and Return String Data in Java

In Java,  char[] ,  String ,  StringBuffer , and  StringBuilder are used to store, take, and return string data. One question that may come to your mind is, "What is the best way for defining a method to take string data and return string data in Java?"

We have four ways to take and return string data:
1) char[]/byte[]
2) String
3) StringBuilder
4) StringBuffer