Methods for the ListNode class will consist of those for creating, accessing, and modifying nodes.

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

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

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

ListNode 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.

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

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

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

ListNode list;

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

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

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


Run Output:

The node contains: 13
The node contains: 17