ListIterator Class

Article
04/11/2014

The ListIterator class is used to iterate over the elements in a list.

Syntax

class ListIterator extends Object

Run On

Called

Methods

	Method	Description
	begin	Moves the iterator to the start of the list.
	cancelTimeOut	Cancels a previous method call to the setTimeOut method. (Inherited from Object.)
	definitionString	Returns a textual representation of the type of the iterator.
	delete	Removes the element that is pointed to by the iterator from the list.
	end	Moves the iterator past the last element in the list.
	equal	Determines whether the specified object is equal to the current one. (Inherited from Object.)
	getTimeOutTimerHandle	Returns the timer handle for the object. (Inherited from Object.)
	handle	Retrieves the handle of the class of the object. (Inherited from Object.)
	insert	Inserts a new value at the position in the list that the iterator currently points to.
	more	Determines whether the list iterator points to a valid element.
	new	Creates a new iterator for a particular list. (Overrides the new Method.)
	next	Moves the iterator to the next element in the list.
	notify	Releases the hold on an object that has called the wait method on this object. (Inherited from Object.)
	notifyAll	Releases a lock on the object that was issued by the wait method on this object. (Inherited from Object.)
	objectOnServer	Determines whether the object is on a server. (Inherited from Object.)
	owner	Returns the instance that owns the object. (Inherited from Object.)
	setTimeOut	Sets up the scheduled execution of a specified method. (Inherited from Object.)
	toString	Returns a textual representation of the current list value that is pointed to by the iterator. (Overrides the toString Method.)
	usageCount	Returns the current number of references, that is, the value of the reference counter, that the object has. (Inherited from Object.)
	value	Retrieves the value that is pointed to by the iterator.
	wait	Pauses a process. (Inherited from Object.)
	xml	Returns an XML string that represents the current object. (Inherited from Object.)

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Remarks

List iterators can be viewed as pointers into the lists over which they iterate. Functionality is available to start the iteration, determine whether more elements are available, and fetch the element that is pointed to by the iterator.

The order in which the elements occur during iteration is defined by the sequence in which the elements are inserted. Elements can be inserted by using the List.addStart, List.addEnd, or ListIterator.insert method.

It is better to use the ListEnumerator class than the ListIterator class. List iterators and the maps over which they iterate must be on the same client/server side. If you use the ListIterator class, and code is marked as Called from, it is possible that the list and the iterator will be on different tiers. In this case, the code will fail.

If you use the ListEnumerator class, the enumerator is automatically created on the same tier as the list. Additionally, to move to the next item in a list, you must explicitly call the more and next methods if you are using a list iterator. If you use the ListEnumerator class, you only have to call the moveNext method.

The only situation where you cannot use a list enumerator is where you need to delete elements from a list. For more information, see the delete method.

Examples

The following example creates a list and an iterator to point to it. It then uses various methods on the ListIterator class to print a description of the list, and the items in the list.

{ 
    List il = new List(types::Integer); 
    ListIterator it; 
  
    // Add some elements into the list. 
    il.addStart(1); 
    il.addStart(2); 
    il.addStart(4);  
  
    // Create a list iterator to traverse the values. 
    it = new ListIterator (il);  
  
    // Prints "int list iterator". 
    print it.definitionString();  
    // Prints "(begin)[4]". 
    print it.toString();  
  
    // Go on for as long as elements are found in the list. 
    // Prints 4, 2, 1. 
    while (it.more()) 
    { 
        print it.value(); 
        it.next(); 
    } 
    // Prints (end). 
    print it.toString(); 
    pause; 
}

Inheritance Hierarchy

Object Class
ListIterator Class

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