Part A B and C

Oucstion i This question is about object oriented programming and ArrayLists (20 points total) We wish to implement our own version of a mutable modified (unlike the Java immutable String). We structure. It will be your job to implement this class and to fill in the missing in will use an ArrayList as our underlying public Mutablestring implements IterablecCharacters ( private ArrayList characters: //a constructor that creates a mutable string from a starting //Java String public MutableString(String str) 2 //a constructor that creates an empty mutable string. public Mutablestring) f //a method that returns the character at index "index" if it exists and throws an appropriate exception if it doesn't exist. public char get (int index)