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/*

* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.

* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.

*

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package java.util;

import java.util.function.Consumer;

/**

* An iterator over a collection. {@code Iterator} takes the place of

* {@link Enumeration} in the Java Collections Framework. Iterators

* differ from enumerations in two ways:

*

* <ul>

* <li> Iterators allow the caller to remove elements from the

* underlying collection during the iteration with well-defined

* semantics.

* <li> Method names have been improved.

* </ul>

*

* <p>This interface is a member of the

* <a href="{@docRoot}/../technotes/guides/collections/index.html">

* Java Collections Framework</a>.

*

* @param <E> the type of elements returned by this iterator

*

* @author Josh Bloch

* @see Collection

* @see ListIterator

* @see Iterable

* @since 1.2

*/

public interface Iterator<E> {

/**

* Returns {@code true} if the iteration has more elements.

* (In other words, returns {@code true} if {@link #next} would

* return an element rather than throwing an exception.)

*

* @return {@code true} if the iteration has more elements

*/

boolean hasNext();

/**

* Returns the next element in the iteration.

*

* @return the next element in the iteration

* @throws NoSuchElementException if the iteration has no more elements

*/

E next();

/**

* Removes from the underlying collection the last element returned

* by this iterator (optional operation). This method can be called

* only once per call to {@link #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.

*

* @implSpec

* The default implementation throws an instance of

* {@link UnsupportedOperationException} and performs no other action.

*

* @throws UnsupportedOperationException if the {@code remove}

* operation is not supported by this iterator

*

* @throws IllegalStateException if the {@code next} method has not

* yet been called, or the {@code remove} method has already

* been called after the last call to the {@code next}

* method

*/

default void remove() {

throw new UnsupportedOperationException("remove");

}

/**

* 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.

*

* @implSpec

* <p>The default implementation behaves as if:

* <pre>{@code

* while (hasNext())

* action.accept(next());

* }</pre>

*

* @param action The action to be performed for each element

* @throws NullPointerException if the specified action is null

* @since 1.8

*/

default void forEachRemaining(Consumer<? super E> action) {

Objects.requireNonNull(action);

while (hasNext())

action.accept(next());

}

}