exercises for source code and help with exercisesplease visit java datastructures net reinforcement - the add and remove methods of code fragments and do not keep track of the number,nof non-null entries in the arraya insteadthe unused cells point to the null object show how to change these methods so that they keep track of the actual size of in an instance variable - describe way to use recursion to add all the elements in (two dimensionalarray of integers - explain how to modify the caesar cipher program (code fragment so that it performs rot encryption and decryptionwhich uses as the alphabet shift amount how can you further simplify the code so that the body of the decrypt method is only single liner- explain the changes that would have be made to the program of code fragment so that it could perform the caesar cipher for messages that are written in an alphabet-based language other than englishsuch as greekrussianor hebrew - what is the exception that is thrown when advance or remove is called on an empty listfrom code fragment explain how to modify these methods so that they give more instructive exception name for this condition - give recursive definition of singly linked list - describe method for inserting an element at the beginning of singly linked list assume that the list does not have sentinel header nodeand instead uses variable head to reference the first node in the list