Package com.google.common.collect

Interface PeekingIterator<E extends @Nullable Object>

All Superinterfaces:

Iterator<E>

@DoNotMock("Use Iterators.peekingIterator")
@GwtCompatible
public interface PeekingIterator<E extends @Nullable Object>
extends Iterator<E>

An iterator that supports a one-element lookahead while iterating.

See the Guava User Guide article on PeekingIterator.

Since:

2.0

Author:

Mick Killianey

Method Summary

Modifier and Type	Method	Description
E	next()	Returns the next element in the iteration.
E	peek()	Returns the next element in the iteration, without advancing the iteration.
void	remove()	Removes from the underlying collection the last element returned by this iterator (optional operation).

Methods inherited from interface java.util.Iterator

forEachRemaining, hasNext

Method Detail

peek

E peek()

Returns the next element in the iteration, without advancing the iteration.

Calls to peek() should not change the state of the iteration, except that it may prevent removal of the most recent element via remove().

Throws:

NoSuchElementException - if the iteration has no more elements according to Iterator.hasNext()

next

@CanIgnoreReturnValue
E next()

Returns the next element in the iteration.

The objects returned by consecutive calls to peek() then next() are guaranteed to be equal to each other.

Specified by:

next in interface Iterator<E extends @Nullable Object>

Returns:

the next element in the iteration

remove

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 Iterator.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.

Implementations may or may not support removal when a call to peek() has occurred since the most recent call to next().

Specified by:

remove in interface Iterator<E extends @Nullable Object>

Throws:

IllegalStateException - if there has been a call to peek() since the most recent call to next() and this implementation does not support this sequence of calls (optional)