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119 lines
3.3 KiB
119 lines
3.3 KiB
/*
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* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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package java.util;
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import java.util.function.Consumer;
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/**
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* An iterator over a collection. {@code Iterator} takes the place of
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* {@link Enumeration} in the Java Collections Framework. Iterators
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* differ from enumerations in two ways:
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*
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* <ul>
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* <li> Iterators allow the caller to remove elements from the
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* underlying collection during the iteration with well-defined
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* semantics.
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* <li> Method names have been improved.
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* </ul>
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*
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* <p>This interface is a member of the
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* <a href="{@docRoot}/../technotes/guides/collections/index.html">
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* Java Collections Framework</a>.
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*
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* @param <E> the type of elements returned by this iterator
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*
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* @author Josh Bloch
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* @see Collection
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* @see ListIterator
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* @see Iterable
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* @since 1.2
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*/
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public interface Iterator<E> {
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/**
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* Returns {@code true} if the iteration has more elements.
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* (In other words, returns {@code true} if {@link #next} would
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* return an element rather than throwing an exception.)
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*
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* @return {@code true} if the iteration has more elements
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*/
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boolean hasNext();
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/**
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* Returns the next element in the iteration.
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*
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* @return the next element in the iteration
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* @throws NoSuchElementException if the iteration has no more elements
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*/
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E next();
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/**
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* Removes from the underlying collection the last element returned
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* by this iterator (optional operation). This method can be called
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* only once per call to {@link #next}. The behavior of an iterator
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* is unspecified if the underlying collection is modified while the
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* iteration is in progress in any way other than by calling this
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* method.
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*
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* @implSpec
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* The default implementation throws an instance of
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* {@link UnsupportedOperationException} and performs no other action.
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*
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* @throws UnsupportedOperationException if the {@code remove}
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* operation is not supported by this iterator
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*
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* @throws IllegalStateException if the {@code next} method has not
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* yet been called, or the {@code remove} method has already
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* been called after the last call to the {@code next}
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* method
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*/
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default void remove() {
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throw new UnsupportedOperationException("remove");
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}
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/**
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* Performs the given action for each remaining element until all elements
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* have been processed or the action throws an exception. Actions are
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* performed in the order of iteration, if that order is specified.
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* Exceptions thrown by the action are relayed to the caller.
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*
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* @implSpec
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* <p>The default implementation behaves as if:
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* <pre>{@code
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* while (hasNext())
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* action.accept(next());
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* }</pre>
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*
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* @param action The action to be performed for each element
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* @throws NullPointerException if the specified action is null
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* @since 1.8
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*/
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default void forEachRemaining(Consumer<? super E> action) {
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Objects.requireNonNull(action);
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while (hasNext())
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action.accept(next());
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}
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}
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