HW 4 Queue class implemented using a doubly-linked list

The basics of a Queue class implemented using a doubly-linked list is provided. See
DoublyLinked Queue.java under General Resources in piazza.
Your assigment is to complete the following methods (other required methods are already
in the file)
! enqueue
! dequeue
! display method
Finally, write a main method that demonstrates that your queue works as it should