Apache Commons Collections 4.4 · org.apache.commons.collections4.iterators.PeekingIterator

Modifier and Type	Field and Description
private boolean	exhausted Indicates that the decorated iterator is exhausted.
private final 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.

Access	Constructor and Description
public	PeekingIterator(final Iterator<? extends E> the iterator to decorate iterator) Constructor.

Method Summary

Modifier and Type	Method and Description
public E	Returns: the next element from the iterator element() Returns the next element in iteration without advancing the underlying iterator.
private void	fill()
public boolean	hasNext() Implements java.util.Iterator.hasNext. Returns `true` if the iteration has more elements.
public E	next() Implements java.util.Iterator.next. Returns the next element in the iteration.
public E	Returns: the next element from the iterator peek() Returns the next element in iteration without advancing the underlying iterator.
public static < the element type E> PeekingIterator<E>	Returns: a new peeking iterator peekingIterator(final Iterator<? extends E> the iterator to decorate iterator) Decorates the specified iterator to support one-element lookahead.
public void	remove() Overrides default java.util.Iterator.remove. Removes from the underlying collection the last element returned by this iterator (optional operation).

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

exhausted	back to summary
private boolean exhausted Indicates that the decorated iterator is exhausted.

iterator	back to summary
private final Iterator<? extends E> iterator The iterator being decorated.

slot	back to summary
private E slot The current slot for lookahead.

slotFilled	back to summary
private boolean slotFilled Indicates if the lookahead slot is filled.

PeekingIterator	back to summary
public PeekingIterator(final Iterator<? extends E> iterator) Constructor. Parameters iterator:Iterator<? extends E> the iterator to decorate

Method Detail

element back to summary

element	back to summary
public E element() Returns the next element in iteration without advancing the underlying iterator. If the iterator is already exhausted, null will be returned. Returns:E the next element from the iterator Exceptions NoSuchElementException: if the iterator is already exhausted according to `hasNext()`

public E element()

Returns the next element in iteration without advancing the underlying iterator. If the iterator is already exhausted, null will be returned.

Returns:E

the next element from the iterator

Exceptions

NoSuchElementException:: if the iterator is already exhausted according to hasNext()

fill	back to summary
private void fill()

hasNext back to summary

hasNext	back to summary
public boolean hasNext() Implements java.util.Iterator.hasNext. Doc from java.util.Iterator.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 Annotations @Override

public boolean hasNext()

Implements java.util.Iterator.hasNext.

Doc from java.util.Iterator.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

Annotations

@Override

next	back to summary
public E next() Implements java.util.Iterator.next. Doc from java.util.Iterator.next. Returns the next element in the iteration. Returns:E the next element in the iteration Annotations @Override

back to summary

public E next()

Implements java.util.Iterator.next.

Doc from java.util.Iterator.next.

Returns the next element in the iteration.

Returns:E

the next element in the iteration

Annotations

@Override

peek back to summary

peek	back to summary
public E peek() Returns the next element in iteration without advancing the underlying iterator. If the iterator is already exhausted, null will be returned. 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 `java.util.Queue` interface which uses the same terminology. Returns:E the next element from the iterator

public E peek()

Returns the next element in iteration without advancing the underlying iterator. If the iterator is already exhausted, null will be returned.

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 java.util.Queue interface which uses the same terminology.

Returns:E: the next element from the iterator

peekingIterator back to summary

peekingIterator	back to summary
public static <E> PeekingIterator<E> peekingIterator(final Iterator<? extends E> iterator) Decorates the specified iterator to support one-element lookahead. If the iterator is already a `PeekingIterator` it is returned directly. Parameters <E> the element type iterator:Iterator<? extends E> the iterator to decorate Returns:PeekingIterator<E> a new peeking iterator Exceptions NullPointerException: if the iterator is null

public static <E> PeekingIterator<E> peekingIterator(final Iterator<? extends E> iterator)

Decorates the specified iterator to support one-element lookahead.

If the iterator is already a PeekingIterator it is returned directly.

Parameters

<E>: the element type
iterator:Iterator<? extends E>: the iterator to decorate

Returns:PeekingIterator<E>

a new peeking iterator

Exceptions

NullPointerException:: if the iterator is null

remove back to summary

remove	back to summary
public void remove() Overrides default java.util.Iterator.remove. Doc from java.util.Iterator.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. Annotations @Override Exceptions IllegalStateException: if `peek()` or `element()` has been called prior to the call to `remove()`

public void remove()

Overrides default java.util.Iterator.remove.

Doc from java.util.Iterator.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.

Annotations

@Override

Exceptions

IllegalStateException:: if peek() or element() has been called prior to the call to remove()

public Class PeekingIterator<E>

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail