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 static boolean checkBalance(String expr) \{ // ToDo \}