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 ( );
}
Too many methods to list.