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- 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.Iteratortakes the place ofEnumerationin 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
Enumerationcan be converted into anIteratorby using theEnumeration.asIterator()method. - Since:
- 1.2
- See Also:
Collection,ListIterator,Iterable
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Method Summary
All Methods Instance Methods Abstract Methods Default Methods Modifier and Type Method Description default voidforEachRemaining(Consumer<? super E> action)Performs the given action for each remaining element until all elements have been processed or the action throws an exception.booleanhasNext()Returnstrueif the iteration has more elements.Enext()Returns the next element in the iteration.default voidremove()Removes from the underlying collection the last element returned by this iterator (optional operation).
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Method Detail
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hasNext
boolean hasNext()
Returnstrueif the iteration has more elements. (In other words, returnstrueifnext()would return an element rather than throwing an exception.)- Returns:
trueif the iteration has more elements
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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
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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 tonext().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
forEachRemainingmethod.- Implementation Requirements:
- The default implementation throws an instance of
UnsupportedOperationExceptionand performs no other action. - Throws:
UnsupportedOperationException- if theremoveoperation is not supported by this iteratorIllegalStateException- if thenextmethod has not yet been called, or theremovemethod has already been called after the last call to thenextmethod
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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
removemethod or other mutator methods ofIteratorsubtypes), 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
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