package DataStructures; // LinkedListItr class; maintains "current position" // // CONSTRUCTION: Package friendly only, with a ListNode // // ******************PUBLIC OPERATIONS********************* // void advance( ) --> Advance // boolean isPastEnd( ) --> True if at "null" position in list // Object retrieve --> Return item in current position /** * Linked list implementation of the list iterator * using a header node. * @author Mark Allen Weiss * @see LinkedList */ public class LinkedListItr { /** * Construct the list iterator * @param theNode any node in the linked list. */ LinkedListItr( ListNode theNode ) { current = theNode; } /** * Test if the current position is past the end of the list. * @return true if the current position is null. */ public boolean isPastEnd( ) { return current == null; } /** * Return the item stored in the current position. * @return the stored item or null if the current position * is not in the list. */ public Object retrieve( ) { return isPastEnd( ) ? null : current.element; } /** * Advance the current position to the next node in the list. * If the current position is null, then do nothing. */ public void advance( ) { if( !isPastEnd( ) ) current = current.next; } ListNode current; // Current position }