Stack based LinkedList implementation 1. Go to the List interface and add a method to get the value of the head You should also add the implementation of the method the the LinkedList and DoublyLinkedList classes. public E getHead( ) if (! empty ()) return head. data; return null; \} 2. The Stack class class Stack implements StackADT // ToDo \} Implementing the checkBalance method Given an expression string exp, write a program to examine whether the pairs and the orders of "\{ {,,"(",)","[,"] " are correct in exp. static boolean checkBalance(string expr) \{ // ToDo \}