Hello. Please add a toString() function to the Java class implementation of the singly-linked list which returns the contents of the singly-linked list. Also, does Java have a built-in class that implements singly-linked lists? Thank you.

Hello. Please add a toString() function to the Java class implementation of the singly-linked list which returns the contents of the singly-linked list. Also, does Java have a built-in class that implements singly-linked lists? Thank you.

public class SinglyLinkedList<E>
{
   private static class Node<E>
   {
      private E element;
      private Node<E> next;
      
      public Node(E e, Node<E> n)
      {
         element = e;
         next = n;
      }   
      
      public E getElement() { return element;}
      public Node<E> getNext() { return next;} 
      public void setNext(Node<E> n) { next = n;}
   }
      
   private Node<E> head = null;
   private Node<E> tail = null;
   private int size = 0;
   public SinglyLinkedList() {}
   public int size() { return size;}
   public boolean isEmpty() { return size == 0;}
      
   public E first() 
   {
      if(isEmpty()) return null;
      return head.getElement();
   }
      
   public E last() 
   {
      if(isEmpty()) return null;
      return tail.getElement();
   }
      
   public void addFirst(E e) 
   {
      head = new Node<>(e, head);
      if(size == 0)
         tail = head;
      size++;
   }
      
   public void addLast(E e) 
   {
      Node<E> newest = new Node<>(e, null);
      if(isEmpty())
         head = newest;
      else
         tail.setNext(newest);
      tail = newest;
      size++;
   }
      
   public E removeFirst() 
   {
      if(isEmpty()) return null;
      E answer = head.getElement();
      head = head.getNext();
      size--;
         
      if(size == 0)
         tail = null;
      return answer;
   }

}