Build Both Ends of a Linked Queue

LinkedQueue adds at the tail and removes at the head, so the two missing methods must keep head, tail and size telling the same story.

Requirements:
1. enqueue(int value): link a new Node on at the tail, point head and tail at it when the queue was empty, and grow size.
2. dequeue(): return -1 when empty, otherwise save head.value, move head on, shrink size and return the saved value.
3. When dequeue() removes the last node, tail must go back to null - otherwise the next enqueue hangs off a node that has left the queue and the value is lost.

The Node class is provided - do not rename it and do not add public to it, because a Java source file may contain only one public class.

Do NOT write a main method.