IteratorE

Iterator<E>

java.util

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Java 1.2

This interface defines methods for iterating, or enumerating, the elements of a collection. It has been made generic in Java 5.0 and the type variable E represents the type of the elements in the collection. The hasNext( ) method returns true if there are more elements to be enumerated or false if all elements have already been returned. The next ( ) method returns the next element. These two methods make it easy to loop through an iterator with code such as the following:

 for(Iterator i = c.iterator( ); i.hasNext( ); )     processObject(i.next( )); 

In Java 5.0, collections and other classes that can return an Iterator implement the java.lang.Iterable interface, which allows them to be iterated much more simply with the for/in looping statement.

The Iterator interface is much like the Enumeration interface. In Java 1.2, Iterator is preferred over Enumeration because it provides a well-defined way to safely remove elements from a collection while the iteration is in progress. The remove( ) method removes the object most recently returned by next( ) from the collection that is being iterated through. Note, however, that support for remove( ) is optional; if an Iterator does not support remove( ) , it throws a java.lang.UnsupportedOperationException when you call it. While you are iterating through a collection, you are allowed to modify the collection only by calling the remove( ) method of the Iterator . If the collection is modified in any other way while an iteration is ongoing, the Iterator may fail to operate correctly, or it may throw a ConcurrentModificationException .

 public interface  Iterator<E>  {  // Public Instance Methods  boolean  hasNext  ( );        E  next  ( );        void  remove  ( );   } 

Implementations

ListIterator , Scanner

Returned By

Too many methods to list.