object returned but cannot access its methods?

public class Node {
    private Object element;
    private Node next;
    
    public Node()
    {
        this(null,null);
    }
    public Node(Object e, Node n)
    {
        element = e;
        next = n;
    }
    public void setElement(Object newElement)
    {
        element = newElement;
    }
    public void setNext(Node newNext)
    {
        next = newNext;
    }
    public Object getElement()
    {
        return element;
    }
    public Node getNext()
    {
        return next;
    }
   
    }
################################################
 
public class Employee {
    private  int age,empNum;
    private String fName, lName;
    
    public Employee(int empNum, String fName, String lName, int age)
    {
        this.age = age;
        this.empNum = empNum;
        this.fName = fName;
        this.lName = lName;
    }
    
    public String getName()
    {
        String joinName;
        joinName = fName + lName;
        return joinName;
    }
    public int getAge()
    {
        return age;
    }
    public int getEmpNum()
    {
        return empNum;
    }
    @Override
    public String toString()
    {
        return empNum+ "\t" + fName+ " " + lName+ "\t" + age + "\n";
    }
 
}
##################################################
 
public class LinkedQueue 
{
    private Node head, tail;
    private int qSize;
    
    public LinkedQueue()
    {
        head = tail = null;
        qSize = 0;
    }
    public int size()
    {
        return qSize;
    }
    public Node getTail()
    {
        return tail;
    }
    public boolean isEmpty()
    {
    return ( head==tail );
    }
    public Object front() throws QueueEmptyException
    {if (isEmpty())
        throw new QueueEmptyException("Queue is empty");
     else
         return head.getElement();
    }
    
    public void append(Object obj)
    {
    Node node = new Node();
    node.setElement(obj);
    node.setNext(null);
    if(qSize == 0)
        head = node;
    else 
        tail.setNext(node);
    tail = node;
    qSize++;
    }
    public Object serve()throws QueueEmptyException
{
    Object obj;
    if(qSize == 0)
        throw new QueueEmptyException("Queue is empty");
    else 
    {
        obj = head.getElement();
        head = head.getNext();
        qSize--;
    }
    if(qSize == 0)
        tail = null;
    return obj;
    
}
}

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