Implement This Skeleton Code

package jp.co.worksap.global; import java.util.NoSuchElementException; /** * The Queue class represents an immutable first-in-first-out (FIFO) queue of objects. * @param <E> */ public class ImmutableQueue<E> { /** * requires default constructor. */ public ImmutableQueue() { // modify this constructor if necessary, but do not remove default constructor } // add other constructors if necessary /** * Returns the queue that adds an item into the tail of this queue without modifying this queue. *

* e.g.
* When this queue represents the queue (2, 1, 2, 2, 6) and we enqueue the value 4 into this queue,
* this method returns a new queue (2, 1, 2, 2, 6, 4)
* and this object still represents the queue (2, 1, 2, 2, 6) .
* 

* If the element e is null, throws IllegalArgumentException. * @param e * @return * @throws IllegalArgumentException */ public ImmutableQueue<E> enqueue(E e) { return null; } /** * Returns the queue that removes the object at the head of this queue without modifying this queue. *

* e.g.
* When this queue represents the queue (7, 1, 3, 3, 5, 1) ,
* this method returns a new queue (1, 3, 3, 5, 1)
* and this object still represents the queue (7, 1, 3, 3, 5, 1) .
* 

* If this queue is empty, throws java.util.NoSuchElementException. * @return * @throws java.util.NoSuchElementException */ public ImmutableQueue<E> dequeue() { return null; } /** * Looks at the object which is the head of this queue without removing it from the queue. *

* e.g.
* When this queue represents the queue (7, 1, 3, 3, 5, 1),
* this method returns 7 and this object still represents the queue (7, 1, 3, 3, 5, 1)
* 

* If the queue is empty, throws java.util.NoSuchElementException. * @return * @throws java.util.NoSuchElementException */ public E peek() { return null; } /** * Returns the number of objects in this queue. * @return */ public int size() { return -1; } }