In java, Open the String class in the Java API, and take a look at thedifferent versions of the indexOf() and substring() methods,identify what parameters each version of those methods accept andwhat does it return, and do the following: Create a class namedMiniString, the class should have the following: – A private Stringinstance variable named str. – A constructor that takes a String asa parameter and sets the instance variable str to the parameterString. – Create 2 methods each named makeSubstring(), and eachversion of makeSubstring() will implement a version of thesubstring() method from the Java API String class. – Create 4methods each named findIndexOf(), and each version of findIndexOf()will implement a version of the indexOf() method from the Java APIString class. – The only 3 String methods you can use to solve thisproblem are: charAt(), length() and equals(). – IF YOU use anyother method from the String class, you will not get credit forthis problem. – In this problem, you are actually re-inventing thewheel. You are implementing methods that already exist in the JavaAPI. it’s really important to know how those methods work, and howto build them from scratch. . . .