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	/*
	* Licensed to the Apache Software Foundation (ASF) under one or more
	* contributor license agreements. See the NOTICE file distributed with
	* this work for additional information regarding copyright ownership.
	* The ASF licenses this file to You under the Apache License, Version 2.0
	* (the "License"); you may not use this file except in compliance with
	* the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	package org.apache.commons.collections4;

	import java.util.Iterator;

	/**
	* Defines an iterator that operates over a <code>Map</code>.
	* <p>
	* This iterator is a special version designed for maps. It can be more
	* efficient to use this rather than an entry set iterator where the option
	* is available, and it is certainly more convenient.
	* </p>
	* <p>
	* A map that provides this interface may not hold the data internally using
	* Map Entry objects, thus this interface can avoid lots of object creation.
	* </p>
	* <p>
	* In use, this iterator iterates through the keys in the map. After each call
	* to <code>next()</code>, the <code>getValue()</code> method provides direct
	* access to the value. The value can also be set using <code>setValue()</code>.
	* </p>
	* <pre>{@code
	* MapIterator<String,Integer> it = map.mapIterator();
	* while (it.hasNext()) {
	* String key = it.next();
	* Integer value = it.getValue();
	* it.setValue(value + 1);
	* }
	* }</pre>
	*
	* @param <K> the type of the keys in the map
	* @param <V> the type of the values in the map
	* @since 3.0
	*/
	public interface MapIterator<K, V> extends Iterator<K> {

	/**
	* Checks to see if there are more entries still to be iterated.
	*
	* @return <code>true</code> if the iterator has more elements
	*/
	@Override
	boolean hasNext();

	/**
	* Gets the next <em>key</em> from the <code>Map</code>.
	*
	* @return the next key in the iteration
	* @throws java.util.NoSuchElementException if the iteration is finished
	*/
	@Override
	K next();

	//-----------------------------------------------------------------------
	/**
	* Gets the current key, which is the key returned by the last call
	* to <code>next()</code>.
	*
	* @return the current key
	* @throws IllegalStateException if <code>next()</code> has not yet been called
	*/
	K getKey();

	/**
	* Gets the current value, which is the value associated with the last key
	* returned by <code>next()</code>.
	*
	* @return the current value
	* @throws IllegalStateException if <code>next()</code> has not yet been called
	*/
	V getValue();

	//-----------------------------------------------------------------------
	/**
	* Removes the last returned key from the underlying <code>Map</code> (optional operation).
	* <p>
	* This method can be called once per call to <code>next()</code>.
	*
	* @throws UnsupportedOperationException if remove is not supported by the map
	* @throws IllegalStateException if <code>next()</code> has not yet been called
	* @throws IllegalStateException if <code>remove()</code> has already been called
	* since the last call to <code>next()</code>
	*/
	@Override
	void remove();

	/**
	* Sets the value associated with the current key (optional operation).
	*
	* @param value the new value
	* @return the previous value
	* @throws UnsupportedOperationException if setValue is not supported by the map
	* @throws IllegalStateException if <code>next()</code> has not yet been called
	* @throws IllegalStateException if <code>remove()</code> has been called since the
	* last call to <code>next()</code>
	*/
	V setValue(V value);

	}

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