Explain when should we use StringBuilder class instead of the String class.

Whenever any of the methods of String class is used to modify the string, a new object is created and memory is allocated to that object. If there are repeated modifications on the string, the performance can get hampered making it costly. Whereas, the StringBuilder class can be used for modifications over and over again without creating a new object. So one situation where a StringBuilder class might be of use is, if we are manipulation string in a loop.