Name
Iterator<E>
Synopsis
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 ...
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