Methods for the ListNode class will consist of those for creating, accessing, and modifying nodes. An implementation of a generic ListNode class are shown below.

/**
 * Implementation of a node of a singly linked list.
 * 
 * Adapted from the College Board's AP Computer Science AB: Implementation
 * Classes and Interfaces.
 */
public class ListNode<E>
{
   private E value;
   private ListNode next;

   // Constructor
   public ListNode( E initValue, ListNode initNext )
   {
      value = initValue;
      next = initNext;
   }

   // Returns value of list node.
   public E getValue()
   {
      return value;
   }

   // Returns the next field of ListNode.
   public ListNode getNext()
   {
      return next;
   }

    // Sets the value of the list node to theNewValue
   public void setValue( E theNewValue )
   {
      value = theNewValue;
   }

   // Sets the list node's next field to a new reference.
   public void setNext( ListNode theNewNext )
   {
      next = theNewNext;
   }
}

The constructor for the ListNode class is responsible for creating a node and initializing the two instance variables of a new node.

// postcondition: constructs a new element with object initValue,
//                        followed by next element
public ListNode( E initValue, ListNode initNext)
{
  value = initValue;
  next = initNext;
}

Here is an example of code to create the first node of a linked list.

ListNode<Integer> first;
first = new ListNode(new Integer(23), null);

After execution of the two statements, first refers to the header node of a small linked list that contains just one node with the Integer 23.

Getting and setting the data and link of the node are accomplished with getter and setter methods as follows.

// postcondition: returns value associated with this element
public E getValue()
{
  return value;
}

// postcondition: returns reference to next value in list
public ListNode getNext()
{
  return next;
}

public void setValue( E theNewValue )
{
  value = theNewValue;
}

ListNode<Integer> list;

list = new ListNode(new Integer(13), null);

System.out.println("The node contains: " + list.getValue());

list.setValue(new Integer(17));
System.out.println("The node contains: " + list.getValue());


Run Output:

The node contains: 13
The node contains: 17