Cola de Nodos

Interfaz a Utilizar:

package Colas_de_Nodos;

/**
 * @author Daniel Cataño Restrepo <dasniel199410@gmail.com>
 */
public interface INodeQueue<E>{
    public void add(E target);
    public boolean isEmpty();
    public void print();
    public E remove();
}

La clase NodeQueue

package Colas_de_Nodos;

/**
 * @author Daniel Cataño Restrepo <dasniel199410@gmail.com>
 */

public class NodeQueue<E> implements INodeQueue<E>{
    
    private E item;
    private NodeQueue<E> next;
    private NodeQueue<E> raiz, top;
    
    public NodeQueue(E item){
        this.item=item;
    }
    
    public NodeQueue(E item, NodeQueue<E> next){
        this.item=item;
        this.next=next;
    }
    
    public NodeQueue(NodeQueue<E> next){
        this.next=next;
    }
    
    public E getItem() {
        return item;
    }

    public void setItem(E item) {
        this.item = item;
    }

    public NodeQueue<E> getNext() {
        return next;
    }

    public void setNext(NodeQueue<E> next) {
        this.next = next;
    }
    
    public void add(E target) {
        NodeQueue<E> nodoNuevo=new NodeQueue<>(target, null);
        if(isEmpty()){
            raiz=nodoNuevo;
            top=nodoNuevo;
        }else{
            top.next=nodoNuevo;
            top=nodoNuevo;
        }
    }

    public boolean isEmpty() {
        return raiz==null;
    }

    public void print() {
        System.out.print("[");
        for(NodeQueue temp=raiz; temp!=null; temp=temp.next){
            if(temp==top)
                System.out.print(temp.item);
            else
                System.out.print(temp.item+",");            
        }
        System.out.println("]");
    }

    public E remove() {
        if(!isEmpty()){
            E info=raiz.item;
            if(raiz==top){
                raiz=null;
                top=null;
            }else{
                raiz=raiz.next;
            }
            return info;
        }
        return null;
    }    
}

La clase principal

package Colas_de_Nodos;
/**
 * @author Daniel Cataño Restrepo <dasniel199410@gmail.com>
 */
public class Main {

    public static void main(String[] args) {
        NodeQueue cola=new NodeQueue(1);
        cola.add(3);
        cola.add(3);
        cola.add(3);
        cola.add(3);
        cola.add(3);
        cola.add(3);
        cola.print();
        cola.remove();
        cola.print();
        cola.remove();
        cola.print();
        cola.remove();
        cola.print();
        cola.remove();
        cola.print();
        cola.remove();
        cola.print();
        cola.remove();
        cola.print();
        cola.add(3);
        cola.print();
        cola.add(3);
        cola.print();
        cola.add(3);
        cola.print();
        cola.add(3);
        cola.print();
        cola.add(3);
        cola.print();
        cola.add(3);
        cola.print();
    }
}

Lo Que imprime en pantalla: