org.apache.commons.collections4.MapIterator Maven / Gradle / Ivy
/*
* 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 Map.
*
* 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.
*
* 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.
*
* In use, this iterator iterates through the keys in the map. After each call
* to next(), the getValue() method provides direct
* access to the value. The value can also be set using setValue().
*
{@code
* MapIterator it = map.mapIterator();
* while (it.hasNext()) {
* String key = it.next();
* Integer value = it.getValue();
* it.setValue(value + 1);
* }
* }
*
* @param the type of the keys in the map
* @param the type of the values in the map
* @since 3.0
*/
public interface MapIterator extends Iterator {
/**
* Checks to see if there are more entries still to be iterated.
*
* @return true if the iterator has more elements
*/
@Override
boolean hasNext();
/**
* Gets the next key from the Map.
*
* @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 next().
*
* @return the current key
* @throws IllegalStateException if next() has not yet been called
*/
K getKey();
/**
* Gets the current value, which is the value associated with the last key
* returned by next().
*
* @return the current value
* @throws IllegalStateException if next() has not yet been called
*/
V getValue();
//-----------------------------------------------------------------------
/**
* Removes the last returned key from the underlying Map (optional operation).
*
* This method can be called once per call to next().
*
* @throws UnsupportedOperationException if remove is not supported by the map
* @throws IllegalStateException if next() has not yet been called
* @throws IllegalStateException if remove() has already been called
* since the last call to next()
*/
@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 next() has not yet been called
* @throws IllegalStateException if remove() has been called since the
* last call to next()
*/
V setValue(V value);
}