Pila.java

// Cambiar head por tail e usar "https://pastebin.com/F8Dbake1".
public class Pila<T> {
    private NodoPila<Object> head;
    private NodoPila<Object> tail;
    int count;
    public Pila() {
        head=null;
        count=0;
        tail=null;
    }
    //saber pila vacia.
    public boolean empty() {
        return head==null;
    }
    //pushear un elemento a la Pila.
    public void push(Object element) {
        NodoPila<Object> temp = new NodoPila<Object>(element);
      if(count==0) {
          this.head=this.tail=temp;
          ++count;
      }else {
         this.tail.next=temp;
         this.tail=temp;
         ++count;
      }
    }
    //pop un elemento de la Pila.
    public Object pop() {
        if (empty()) {
            throw new RuntimeException("La pila está vacía...");
        }

        Object item = this.tail.data;
        if (this.head.next == null) {
            this.head = this.tail = null;
        } else {
            NodoPila<Object> skip = this.head;
            while (skip.next.next != null) {
                skip = skip.next;
            }
            this.tail = skip;
            this.tail.next = null;
        }
        --this.count;
        return item;


    }
    //peek muestra sin sacar cima de Pila.
    public Object peek() {
        if (empty()) {
            throw new RuntimeException("La pila está vacía...");
        }
        return tail.data;
    }
    //tamaño Pila.
    public int size() {
        return count;
    }
     //region Object Methods

    @Override
    public String toString() {

        if (size() <=0) {
            return "La pila se encuentra Vacia....desu";
        }

        // from https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/lang/StringBuilder.html
        StringBuilder sb = new StringBuilder();
        //Crear tail enlazarlo con el primer modo cargado y utilizarlo para recorre la pila correctamente.
        sb.append("[" + head.data.toString());
        for (NodoPila<?> skip = head.next; skip != null; skip = skip.next) {
            sb.append(", " + skip.data.toString());
        }
        sb.append("]");

        return sb.toString();
    }
    //endregion
}