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Added in API level 1

Iterator

public interface Iterator

java.util.Iterator<E>
Known Indirect Subclasses


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 true if the iteration has more elements.

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

Added in API level 24
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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:
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
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