Interface Iterator<E>
- Type Parameters:
-
E
- the type of elements returned by this iterator
- All Known Subinterfaces:
-
EventIterator
,ListIterator<E>
,PrimitiveIterator<T,T_CONS>
,PrimitiveIterator.OfDouble
,PrimitiveIterator.OfInt
,PrimitiveIterator.OfLong
,XMLEventReader
- All Known Implementing Classes:
-
BeanContextSupport.BCSIterator
,EventReaderDelegate
,Scanner
public interface Iterator<E>
An iterator over a collection. Iterator
takes the place of Enumeration
in the Java Collections Framework. Iterators differ from enumerations in two ways:
- Iterators allow the caller to remove elements from the underlying collection during the iteration with well-defined semantics.
- Method names have been improved.
This interface is a member of the Java Collections Framework.
- API Note:
- An
Enumeration
can be converted into anIterator
by using theEnumeration.asIterator()
method. - Since:
- 1.2
- See Also:
-
Collection
,ListIterator
,Iterable
Method Summary
Modifier and Type | Method | Description |
---|---|---|
default void | forEachRemaining(Consumer<? super E> action) | Performs the given action for each remaining element until all elements have been processed or the action throws an exception. |
boolean | hasNext() | Returns |
E | next() | Returns the next element in the iteration. |
default void | remove() | Removes from the underlying collection the last element returned by this iterator (optional operation). |
Method Detail
hasNext
boolean hasNext()
Returns true
if the iteration has more elements. (In other words, returns true
if next()
would return an element rather than throwing an exception.)
- Returns:
-
true
if the iteration has more elements
next
E next()
Returns the next element in the iteration.
- Returns:
- the next element in the iteration
- Throws:
-
NoSuchElementException
- if the iteration has no more elements
remove
default void remove()
Removes from the underlying collection the last element returned by this iterator (optional operation). This method can be called only once per call to next()
.
The behavior of an iterator is unspecified if the underlying collection is modified while the iteration is in progress in any way other than by calling this method, unless an overriding class has specified a concurrent modification policy.
The behavior of an iterator is unspecified if this method is called after a call to the forEachRemaining
method.
- Implementation Requirements:
- The default implementation throws an instance of
UnsupportedOperationException
and performs no other action. - Throws:
-
UnsupportedOperationException
- if theremove
operation is not supported by this iterator -
IllegalStateException
- if thenext
method has not yet been called, or theremove
method has already been called after the last call to thenext
method
forEachRemaining
default void forEachRemaining(Consumer<? super E> action)
Performs the given action for each remaining element until all elements have been processed or the action throws an exception. Actions are performed in the order of iteration, if that order is specified. Exceptions thrown by the action are relayed to the caller.
The behavior of an iterator is unspecified if the action modifies the collection in any way (even by calling the remove
method or other mutator methods of Iterator
subtypes), unless an overriding class has specified a concurrent modification policy.
Subsequent behavior of an iterator is unspecified if the action throws an exception.
- Implementation Requirements:
-
The default implementation behaves as if:
while (hasNext()) action.accept(next());
- Parameters:
-
action
- The action to be performed for each element - Throws:
-
NullPointerException
- if the specified action is null - Since:
- 1.8