public class PeekingIterator<E>
extends java.lang.Object
implements java.util.Iterator<E>
The decorator supports the removal operation, but an IllegalStateException
will be thrown if remove() is called directly after a call to
peek() or element().
| Modifier and Type | Field and Description |
|---|---|
private boolean |
exhausted
Indicates that the decorated iterator is exhausted.
|
private java.util.Iterator<? extends E> |
iterator
The iterator being decorated.
|
private E |
slot
The current slot for lookahead.
|
private boolean |
slotFilled
Indicates if the lookahead slot is filled.
|
| Constructor and Description |
|---|
PeekingIterator(java.util.Iterator<? extends E> iterator)
Constructor.
|
| Modifier and Type | Method and Description |
|---|---|
E |
element()
Returns the next element in iteration without advancing the underlying iterator.
|
private void |
fill() |
boolean |
hasNext() |
E |
next() |
E |
peek()
Returns the next element in iteration without advancing the underlying iterator.
|
static <E> PeekingIterator<E> |
peekingIterator(java.util.Iterator<? extends E> iterator)
Decorates the specified iterator to support one-element lookahead.
|
void |
remove() |
private final java.util.Iterator<? extends E> iterator
private boolean exhausted
private boolean slotFilled
private E slot
public PeekingIterator(java.util.Iterator<? extends E> iterator)
iterator - the iterator to decoratepublic static <E> PeekingIterator<E> peekingIterator(java.util.Iterator<? extends E> iterator)
If the iterator is already a PeekingIterator it is returned directly.
E - the element typeiterator - the iterator to decoratejava.lang.IllegalArgumentException - if the iterator is nullprivate void fill()
public boolean hasNext()
hasNext in interface java.util.Iterator<E>public E peek()
Note: this method does not throw a NoSuchElementException if the iterator
is already exhausted. If you want such a behavior, use element() instead.
The rationale behind this is to follow the Queue interface
which uses the same terminology.
public E element()
java.util.NoSuchElementException - if the iterator is already exhausted according to hasNext()