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Iterator
public
interface
Iterator
| java.util.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.
See also:
Summary
Public methods | |
|---|---|
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. |
abstract
boolean
|
hasNext()
Returns |
abstract
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). |
Public methods
forEachRemaining
public 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.
Implementation Requirements:
The default implementation behaves as if:
while (hasNext()) action.accept(next());
| Parameters | |
|---|---|
action |
Consumer: The action to be performed for each element |
| Throws | |
|---|---|
NullPointerException |
if the specified action is null |
hasNext
public abstract 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 | |
|---|---|
boolean |
true if the iteration has more elements |
next
public abstract E next ()
Returns the next element in the iteration.
| Returns | |
|---|---|
E |
the next element in the iteration |
| Throws | |
|---|---|
NoSuchElementException |
if the iteration has no more elements |
remove
public 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.
Implementation Requirements:
- The default implementation throws an instance of
UnsupportedOperationExceptionand performs no other action.
| Throws | |
|---|---|
UnsupportedOperationException |
if the remove
operation is not supported by this iterator |
IllegalStateException |
if the next method has not
yet been called, or the remove method has already
been called after the last call to the next
method |