(1) (5 points) A doubly linked list is a linear data structure where (1) each element (called node) is a separate "object" and (2) each node contains three pieces of information - a reference to the previous node, another reference to the next node, and (a reference to) data. Below is an example: The entry point into a doubly linked list is called the front of the list. The front is not a separate node, but a reference to the first node. Similarly, a doubly linked list has a reference (called last) to the last node of the list. You may assume that the data field's type is int. (a) Write a Java program (in file DLList.java) that describes the relationships between the doubly linked list (in class DLList) and node (in class Node)..