/*
* 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.lang.reflect.Array;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.Dictionary;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import org.apache.commons.collections4.functors.EqualPredicate;
import org.apache.commons.collections4.iterators.ArrayIterator;
import org.apache.commons.collections4.iterators.ArrayListIterator;
import org.apache.commons.collections4.iterators.BoundedIterator;
import org.apache.commons.collections4.iterators.CollatingIterator;
import org.apache.commons.collections4.iterators.EmptyIterator;
import org.apache.commons.collections4.iterators.EmptyListIterator;
import org.apache.commons.collections4.iterators.EmptyMapIterator;
import org.apache.commons.collections4.iterators.EmptyOrderedIterator;
import org.apache.commons.collections4.iterators.EmptyOrderedMapIterator;
import org.apache.commons.collections4.iterators.EnumerationIterator;
import org.apache.commons.collections4.iterators.FilterIterator;
import org.apache.commons.collections4.iterators.FilterListIterator;
import org.apache.commons.collections4.iterators.IteratorChain;
import org.apache.commons.collections4.iterators.IteratorEnumeration;
import org.apache.commons.collections4.iterators.IteratorIterable;
import org.apache.commons.collections4.iterators.ListIteratorWrapper;
import org.apache.commons.collections4.iterators.LoopingIterator;
import org.apache.commons.collections4.iterators.LoopingListIterator;
import org.apache.commons.collections4.iterators.NodeListIterator;
import org.apache.commons.collections4.iterators.ObjectArrayIterator;
import org.apache.commons.collections4.iterators.ObjectArrayListIterator;
import org.apache.commons.collections4.iterators.ObjectGraphIterator;
import org.apache.commons.collections4.iterators.PeekingIterator;
import org.apache.commons.collections4.iterators.PushbackIterator;
import org.apache.commons.collections4.iterators.SingletonIterator;
import org.apache.commons.collections4.iterators.SingletonListIterator;
import org.apache.commons.collections4.iterators.SkippingIterator;
import org.apache.commons.collections4.iterators.TransformIterator;
import org.apache.commons.collections4.iterators.UnmodifiableIterator;
import org.apache.commons.collections4.iterators.UnmodifiableListIterator;
import org.apache.commons.collections4.iterators.UnmodifiableMapIterator;
import org.apache.commons.collections4.iterators.ZippingIterator;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
/**
* Provides static utility methods and decorators for {@link Iterator}
* instances. The implementations are provided in the iterators subpackage.
*
* @since 2.1
* @version $Id$
*/
public class IteratorUtils {
// validation is done in this class in certain cases because the
// public classes allow invalid states
/**
* An iterator over no elements.
*/
@SuppressWarnings("rawtypes")
public static final ResettableIterator EMPTY_ITERATOR = EmptyIterator.RESETTABLE_INSTANCE;
/**
* A list iterator over no elements.
*/
@SuppressWarnings("rawtypes")
public static final ResettableListIterator EMPTY_LIST_ITERATOR = EmptyListIterator.RESETTABLE_INSTANCE;
/**
* An ordered iterator over no elements.
*/
@SuppressWarnings("rawtypes")
public static final OrderedIterator EMPTY_ORDERED_ITERATOR = EmptyOrderedIterator.INSTANCE;
/**
* A map iterator over no elements.
*/
@SuppressWarnings("rawtypes")
public static final MapIterator EMPTY_MAP_ITERATOR = EmptyMapIterator.INSTANCE;
/**
* An ordered map iterator over no elements.
*/
@SuppressWarnings("rawtypes")
public static final OrderedMapIterator EMPTY_ORDERED_MAP_ITERATOR = EmptyOrderedMapIterator.INSTANCE;
/**
* Default prefix used while converting an Iterator to its String representation.
*/
private static final String DEFAULT_TOSTRING_PREFIX = "[";
/**
* Default suffix used while converting an Iterator to its String representation.
*/
private static final String DEFAULT_TOSTRING_SUFFIX = "]";
/**
* Default delimiter used to delimit elements while converting an Iterator
* to its String representation.
*/
private static final String DEFAULT_TOSTRING_DELIMITER = ", ";
/**
* IteratorUtils is not normally instantiated.
*/
private IteratorUtils() {}
// Empty
//-----------------------------------------------------------------------
/**
* Gets an empty iterator.
* <p>
* This iterator is a valid iterator object that will iterate over nothing.
*
* @param <E> the element type
* @return an iterator over nothing
*/
public static <E> ResettableIterator<E> emptyIterator() {
return EmptyIterator.<E>resettableEmptyIterator();
}
/**
* Gets an empty list iterator.
* <p>
* This iterator is a valid list iterator object that will iterate
* over nothing.
*
* @param <E> the element type
* @return a list iterator over nothing
*/
public static <E> ResettableListIterator<E> emptyListIterator() {
return EmptyListIterator.<E>resettableEmptyListIterator();
}
/**
* Gets an empty ordered iterator.
* <p>
* This iterator is a valid iterator object that will iterate
* over nothing.
*
* @param <E> the element type
* @return an ordered iterator over nothing
*/
public static <E> OrderedIterator<E> emptyOrderedIterator() {
return EmptyOrderedIterator.<E>emptyOrderedIterator();
}
/**
* Gets an empty map iterator.
* <p>
* This iterator is a valid map iterator object that will iterate
* over nothing.
*
* @param <K> the key type
* @param <V> the value type
* @return a map iterator over nothing
*/
public static <K, V> MapIterator<K, V> emptyMapIterator() {
return EmptyMapIterator.<K, V>emptyMapIterator();
}
/**
* Gets an empty ordered map iterator.
* <p>
* This iterator is a valid map iterator object that will iterate
* over nothing.
*
* @param <K> the key type
* @param <V> the value type
* @return a map iterator over nothing
*/
public static <K, V> OrderedMapIterator<K, V> emptyOrderedMapIterator() {
return EmptyOrderedMapIterator.<K, V>emptyOrderedMapIterator();
}
// Singleton
//-----------------------------------------------------------------------
/**
* Gets a singleton iterator.
* <p>
* This iterator is a valid iterator object that will iterate over
* the specified object.
*
* @param <E> the element type
* @param object the single object over which to iterate
* @return a singleton iterator over the object
*/
public static <E> ResettableIterator<E> singletonIterator(final E object) {
return new SingletonIterator<E>(object);
}
/**
* Gets a singleton list iterator.
* <p>
* This iterator is a valid list iterator object that will iterate over
* the specified object.
*
* @param <E> the element type
* @param object the single object over which to iterate
* @return a singleton list iterator over the object
*/
public static <E> ListIterator<E> singletonListIterator(final E object) {
return new SingletonListIterator<E>(object);
}
// Arrays
//-----------------------------------------------------------------------
/**
* Gets an iterator over an object array.
*
* @param <E> the element type
* @param array the array over which to iterate
* @return an iterator over the array
* @throws NullPointerException if array is null
*/
public static <E> ResettableIterator<E> arrayIterator(final E... array) {
return new ObjectArrayIterator<E>(array);
}
/**
* Gets an iterator over an object or primitive array.
* <p>
* This method will handle primitive arrays as well as object arrays.
* The primitives will be wrapped in the appropriate wrapper class.
*
* @param <E> the element type
* @param array the array over which to iterate
* @return an iterator over the array
* @throws IllegalArgumentException if the array is not an array
* @throws NullPointerException if array is null
*/
public static <E> ResettableIterator<E> arrayIterator(final Object array) {
return new ArrayIterator<E>(array);
}
/**
* Gets an iterator over the end part of an object array.
*
* @param <E> the element type
* @param array the array over which to iterate
* @param start the index to start iterating at
* @return an iterator over part of the array
* @throws IndexOutOfBoundsException if start is less than zero or greater
* than the length of the array
* @throws NullPointerException if array is null
*/
public static <E> ResettableIterator<E> arrayIterator(final E[] array, final int start) {
return new ObjectArrayIterator<E>(array, start);
}
/**
* Gets an iterator over the end part of an object or primitive array.
* <p>
* This method will handle primitive arrays as well as object arrays.
* The primitives will be wrapped in the appropriate wrapper class.
*
* @param <E> the element type
* @param array the array over which to iterate
* @param start the index to start iterating at
* @return an iterator over part of the array
* @throws IllegalArgumentException if the array is not an array
* @throws IndexOutOfBoundsException if start is less than zero or greater
* than the length of the array
* @throws NullPointerException if array is null
*/
public static <E> ResettableIterator<E> arrayIterator(final Object array, final int start) {
return new ArrayIterator<E>(array, start);
}
/**
* Gets an iterator over part of an object array.
*
* @param <E> the element type
* @param array the array over which to iterate
* @param start the index to start iterating at
* @param end the index to finish iterating at
* @return an iterator over part of the array
* @throws IndexOutOfBoundsException if array bounds are invalid
* @throws IllegalArgumentException if end is before start
* @throws NullPointerException if array is null
*/
public static <E> ResettableIterator<E> arrayIterator(final E[] array, final int start, final int end) {
return new ObjectArrayIterator<E>(array, start, end);
}
/**
* Gets an iterator over part of an object or primitive array.
* <p>
* This method will handle primitive arrays as well as object arrays.
* The primitives will be wrapped in the appropriate wrapper class.
*
* @param <E> the element type
* @param array the array over which to iterate
* @param start the index to start iterating at
* @param end the index to finish iterating at
* @return an iterator over part of the array
* @throws IllegalArgumentException if the array is not an array or end is before start
* @throws IndexOutOfBoundsException if array bounds are invalid
* @throws NullPointerException if array is null
*/
public static <E> ResettableIterator<E> arrayIterator(final Object array, final int start, final int end) {
return new ArrayIterator<E>(array, start, end);
}
//-----------------------------------------------------------------------
/**
* Gets a list iterator over an object array.
*
* @param <E> the element type
* @param array the array over which to iterate
* @return a list iterator over the array
* @throws NullPointerException if array is null
*/
public static <E> ResettableListIterator<E> arrayListIterator(final E... array) {
return new ObjectArrayListIterator<E>(array);
}
/**
* Gets a list iterator over an object or primitive array.
* <p>
* This method will handle primitive arrays as well as object arrays.
* The primitives will be wrapped in the appropriate wrapper class.
*
* @param <E> the element type
* @param array the array over which to iterate
* @return a list iterator over the array
* @throws IllegalArgumentException if the array is not an array
* @throws NullPointerException if array is null
*/
public static <E> ResettableListIterator<E> arrayListIterator(final Object array) {
return new ArrayListIterator<E>(array);
}
/**
* Gets a list iterator over the end part of an object array.
*
* @param <E> the element type
* @param array the array over which to iterate
* @param start the index to start iterating at
* @return a list iterator over part of the array
* @throws IndexOutOfBoundsException if start is less than zero
* @throws NullPointerException if array is null
*/
public static <E> ResettableListIterator<E> arrayListIterator(final E[] array, final int start) {
return new ObjectArrayListIterator<E>(array, start);
}
/**
* Gets a list iterator over the end part of an object or primitive array.
* <p>
* This method will handle primitive arrays as well as object arrays.
* The primitives will be wrapped in the appropriate wrapper class.
*
* @param <E> the element type
* @param array the array over which to iterate
* @param start the index to start iterating at
* @return a list iterator over part of the array
* @throws IllegalArgumentException if the array is not an array
* @throws IndexOutOfBoundsException if start is less than zero
* @throws NullPointerException if array is null
*/
public static <E> ResettableListIterator<E> arrayListIterator(final Object array, final int start) {
return new ArrayListIterator<E>(array, start);
}
/**
* Gets a list iterator over part of an object array.
*
* @param <E> the element type
* @param array the array over which to iterate
* @param start the index to start iterating at
* @param end the index to finish iterating at
* @return a list iterator over part of the array
* @throws IndexOutOfBoundsException if array bounds are invalid
* @throws IllegalArgumentException if end is before start
* @throws NullPointerException if array is null
*/
public static <E> ResettableListIterator<E> arrayListIterator(final E[] array, final int start, final int end) {
return new ObjectArrayListIterator<E>(array, start, end);
}
/**
* Gets a list iterator over part of an object or primitive array.
* <p>
* This method will handle primitive arrays as well as object arrays.
* The primitives will be wrapped in the appropriate wrapper class.
*
* @param <E> the element type
* @param array the array over which to iterate
* @param start the index to start iterating at
* @param end the index to finish iterating at
* @return a list iterator over part of the array
* @throws IllegalArgumentException if the array is not an array or end is before start
* @throws IndexOutOfBoundsException if array bounds are invalid
* @throws NullPointerException if array is null
*/
public static <E> ResettableListIterator<E> arrayListIterator(final Object array, final int start, final int end) {
return new ArrayListIterator<E>(array, start, end);
}
// Bounded
//-----------------------------------------------------------------------
/**
* Decorates the specified iterator to return at most the given number
* of elements.
*
* @param <E> the element type
* @param iterator the iterator to decorate
* @param max the maximum number of elements returned by this iterator
* @return a new bounded iterator
* @throws NullPointerException if the iterator is null
* @throws IllegalArgumentException if max is negative
* @since 4.1
*/
public static <E> BoundedIterator<E> boundedIterator(final Iterator<? extends E> iterator, long max) {
return boundedIterator(iterator, 0, max);
}
/**
* Decorates the specified iterator to return at most the given number
* of elements, skipping all elements until the iterator reaches the
* position at {@code offset}.
* <p>
* The iterator is immediately advanced until it reaches the position at
* {@code offset}, incurring O(n) time.
*
* @param <E> the element type
* @param iterator the iterator to decorate
* @param offset the index of the first element of the decorated iterator to return
* @param max the maximum number of elements returned by this iterator
* @return a new bounded iterator
* @throws NullPointerException if the iterator is null
* @throws IllegalArgumentException if either offset or max is negative
* @since 4.1
*/
public static <E> BoundedIterator<E> boundedIterator(final Iterator<? extends E> iterator,
long offset, long max) {
return new BoundedIterator<E>(iterator, offset, max);
}
// Unmodifiable
//-----------------------------------------------------------------------
/**
* Gets an immutable version of an {@link Iterator}. The returned object
* will always throw an {@link UnsupportedOperationException} for
* the {@link Iterator#remove} method.
*
* @param <E> the element type
* @param iterator the iterator to make immutable
* @return an immutable version of the iterator
*/
public static <E> Iterator<E> unmodifiableIterator(final Iterator<E> iterator) {
return UnmodifiableIterator.unmodifiableIterator(iterator);
}
/**
* Gets an immutable version of a {@link ListIterator}. The returned object
* will always throw an {@link UnsupportedOperationException} for
* the {@link Iterator#remove}, {@link ListIterator#add} and
* {@link ListIterator#set} methods.
*
* @param <E> the element type
* @param listIterator the iterator to make immutable
* @return an immutable version of the iterator
*/
public static <E> ListIterator<E> unmodifiableListIterator(final ListIterator<E> listIterator) {
return UnmodifiableListIterator.umodifiableListIterator(listIterator);
}
/**
* Gets an immutable version of a {@link MapIterator}. The returned object
* will always throw an {@link UnsupportedOperationException} for
* the {@link Iterator#remove}, {@link MapIterator#setValue(Object)} methods.
*
* @param <K> the key type
* @param <V> the value type
* @param mapIterator the iterator to make immutable
* @return an immutable version of the iterator
*/
public static <K, V> MapIterator<K, V> unmodifiableMapIterator(final MapIterator<K, V> mapIterator) {
return UnmodifiableMapIterator.unmodifiableMapIterator(mapIterator);
}
// Chained
//-----------------------------------------------------------------------
/**
* Gets an iterator that iterates through two {@link Iterator}s
* one after another.
*
* @param <E> the element type
* @param iterator1 the first iterator to use, not null
* @param iterator2 the second iterator to use, not null
* @return a combination iterator over the iterators
* @throws NullPointerException if either iterator is null
*/
public static <E> Iterator<E> chainedIterator(final Iterator<? extends E> iterator1,
final Iterator<? extends E> iterator2) {
// keep a version with two iterators to avoid the following warning in client code (Java 5 & 6)
// "A generic array of E is created for a varargs parameter"
return new IteratorChain<E>(iterator1, iterator2);
}
/**
* Gets an iterator that iterates through an array of {@link Iterator}s
* one after another.
*
* @param <E> the element type
* @param iterators the iterators to use, not null or empty or contain nulls
* @return a combination iterator over the iterators
* @throws NullPointerException if iterators array is null or contains a null
*/
public static <E> Iterator<E> chainedIterator(final Iterator<? extends E>... iterators) {
return new IteratorChain<E>(iterators);
}
/**
* Gets an iterator that iterates through a collections of {@link Iterator}s
* one after another.
*
* @param <E> the element type
* @param iterators the iterators to use, not null or empty or contain nulls
* @return a combination iterator over the iterators
* @throws NullPointerException if iterators collection is null or contains a null
* @throws ClassCastException if the iterators collection contains the wrong object type
*/
public static <E> Iterator<E> chainedIterator(final Collection<Iterator<? extends E>> iterators) {
return new IteratorChain<E>(iterators);
}
// Collated
//-----------------------------------------------------------------------
/**
* Gets an iterator that provides an ordered iteration over the elements
* contained in a collection of ordered {@link Iterator}s.
* <p>
* Given two ordered {@link Iterator}s <code>A</code> and <code>B</code>,
* the {@link Iterator#next()} method will return the lesser of
* <code>A.next()</code> and <code>B.next()</code>.
* <p>
* The comparator is optional. If null is specified then natural order is used.
*
* @param <E> the element type
* @param comparator the comparator to use, may be null for natural order
* @param iterator1 the first iterators to use, not null
* @param iterator2 the first iterators to use, not null
* @return a combination iterator over the iterators
* @throws NullPointerException if either iterator is null
*/
public static <E> Iterator<E> collatedIterator(final Comparator<? super E> comparator,
final Iterator<? extends E> iterator1,
final Iterator<? extends E> iterator2) {
@SuppressWarnings("unchecked")
final Comparator<E> comp =
comparator == null ? ComparatorUtils.NATURAL_COMPARATOR : (Comparator<E>) comparator;
return new CollatingIterator<E>(comp, iterator1, iterator2);
}
/**
* Gets an iterator that provides an ordered iteration over the elements
* contained in an array of {@link Iterator}s.
* <p>
* Given two ordered {@link Iterator}s <code>A</code> and <code>B</code>,
* the {@link Iterator#next()} method will return the lesser of
* <code>A.next()</code> and <code>B.next()</code> and so on.
* <p>
* The comparator is optional. If null is specified then natural order is used.
*
* @param <E> the element type
* @param comparator the comparator to use, may be null for natural order
* @param iterators the iterators to use, not null or empty or contain nulls
* @return a combination iterator over the iterators
* @throws NullPointerException if iterators array is null or contains a null value
*/
public static <E> Iterator<E> collatedIterator(final Comparator<? super E> comparator,
final Iterator<? extends E>... iterators) {
@SuppressWarnings("unchecked")
final Comparator<E> comp =
comparator == null ? ComparatorUtils.NATURAL_COMPARATOR : (Comparator<E>) comparator;
return new CollatingIterator<E>(comp, iterators);
}
/**
* Gets an iterator that provides an ordered iteration over the elements
* contained in a collection of {@link Iterator}s.
* <p>
* Given two ordered {@link Iterator}s <code>A</code> and <code>B</code>,
* the {@link Iterator#next()} method will return the lesser of
* <code>A.next()</code> and <code>B.next()</code> and so on.
* <p>
* The comparator is optional. If null is specified then natural order is used.
*
* @param <E> the element type
* @param comparator the comparator to use, may be null for natural order
* @param iterators the iterators to use, not null or empty or contain nulls
* @return a combination iterator over the iterators
* @throws NullPointerException if iterators collection is null or contains a null
* @throws ClassCastException if the iterators collection contains the wrong object type
*/
public static <E> Iterator<E> collatedIterator(final Comparator<? super E> comparator,
final Collection<Iterator<? extends E>> iterators) {
@SuppressWarnings("unchecked")
final Comparator<E> comp =
comparator == null ? ComparatorUtils.NATURAL_COMPARATOR : (Comparator<E>) comparator;
return new CollatingIterator<E>(comp, iterators);
}
// Object Graph
//-----------------------------------------------------------------------
/**
* Gets an iterator that operates over an object graph.
* <p>
* This iterator can extract multiple objects from a complex tree-like object graph.
* The iteration starts from a single root object.
* It uses a <code>Transformer</code> to extract the iterators and elements.
* Its main benefit is that no intermediate <code>List</code> is created.
* <p>
* For example, consider an object graph:
* <pre>
* |- Branch -- Leaf
* | \- Leaf
* |- Tree | /- Leaf
* | |- Branch -- Leaf
* Forest | \- Leaf
* | |- Branch -- Leaf
* | | \- Leaf
* |- Tree | /- Leaf
* |- Branch -- Leaf
* |- Branch -- Leaf</pre>
* The following <code>Transformer</code>, used in this class, will extract all
* the Leaf objects without creating a combined intermediate list:
* <pre>
* public Object transform(Object input) {
* if (input instanceof Forest) {
* return ((Forest) input).treeIterator();
* }
* if (input instanceof Tree) {
* return ((Tree) input).branchIterator();
* }
* if (input instanceof Branch) {
* return ((Branch) input).leafIterator();
* }
* if (input instanceof Leaf) {
* return input;
* }
* throw new ClassCastException();
* }</pre>
* <p>
* Internally, iteration starts from the root object. When next is called,
* the transformer is called to examine the object. The transformer will return
* either an iterator or an object. If the object is an Iterator, the next element
* from that iterator is obtained and the process repeats. If the element is an object
* it is returned.
* <p>
* Under many circumstances, linking Iterators together in this manner is
* more efficient (and convenient) than using nested for loops to extract a list.
*
* @param <E> the element type
* @param root the root object to start iterating from, null results in an empty iterator
* @param transformer the transformer to use, see above, null uses no effect transformer
* @return a new object graph iterator
* @since 3.1
*/
public static <E> Iterator<E> objectGraphIterator(final E root,
final Transformer<? super E, ? extends E> transformer) {
return new ObjectGraphIterator<E>(root, transformer);
}
// Transformed
//-----------------------------------------------------------------------
/**
* Gets an iterator that transforms the elements of another iterator.
* <p>
* The transformation occurs during the next() method and the underlying
* iterator is unaffected by the transformation.
*
* @param <I> the input type
* @param <O> the output type
* @param iterator the iterator to use, not null
* @param transform the transform to use, not null
* @return a new transforming iterator
* @throws NullPointerException if either parameter is null
*/
public static <I, O> Iterator<O> transformedIterator(final Iterator<? extends I> iterator,
final Transformer<? super I, ? extends O> transform) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
if (transform == null) {
throw new NullPointerException("Transformer must not be null");
}
return new TransformIterator<I, O>(iterator, transform);
}
// Filtered
//-----------------------------------------------------------------------
/**
* Gets an iterator that filters another iterator.
* <p>
* The returned iterator will only return objects that match the specified
* filtering predicate.
*
* @param <E> the element type
* @param iterator the iterator to use, not null
* @param predicate the predicate to use as a filter, not null
* @return a new filtered iterator
* @throws NullPointerException if either parameter is null
*/
public static <E> Iterator<E> filteredIterator(final Iterator<? extends E> iterator,
final Predicate<? super E> predicate) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
if (predicate == null) {
throw new NullPointerException("Predicate must not be null");
}
return new FilterIterator<E>(iterator, predicate);
}
/**
* Gets a list iterator that filters another list iterator.
* <p>
* The returned iterator will only return objects that match the specified
* filtering predicate.
*
* @param <E> the element type
* @param listIterator the list iterator to use, not null
* @param predicate the predicate to use as a filter, not null
* @return a new filtered iterator
* @throws NullPointerException if either parameter is null
*/
public static <E> ListIterator<E> filteredListIterator(final ListIterator<? extends E> listIterator,
final Predicate<? super E> predicate) {
if (listIterator == null) {
throw new NullPointerException("ListIterator must not be null");
}
if (predicate == null) {
throw new NullPointerException("Predicate must not be null");
}
return new FilterListIterator<E>(listIterator, predicate);
}
// Looping
//-----------------------------------------------------------------------
/**
* Gets an iterator that loops continuously over the supplied collection.
* <p>
* The iterator will only stop looping if the remove method is called
* enough times to empty the collection, or if the collection is empty
* to start with.
*
* @param <E> the element type
* @param coll the collection to iterate over, not null
* @return a new looping iterator
* @throws NullPointerException if the collection is null
*/
public static <E> ResettableIterator<E> loopingIterator(final Collection<? extends E> coll) {
if (coll == null) {
throw new NullPointerException("Collection must not be null");
}
return new LoopingIterator<E>(coll);
}
/**
* Gets an iterator that loops continuously over the supplied list.
* <p>
* The iterator will only stop looping if the remove method is called
* enough times to empty the list, or if the list is empty to start with.
*
* @param <E> the element type
* @param list the list to iterate over, not null
* @return a new looping iterator
* @throws NullPointerException if the list is null
* @since 3.2
*/
public static <E> ResettableListIterator<E> loopingListIterator(final List<E> list) {
if (list == null) {
throw new NullPointerException("List must not be null");
}
return new LoopingListIterator<E>(list);
}
// org.w3c.dom.NodeList iterators
//-----------------------------------------------------------------------
/**
* Gets an {@link Iterator} that wraps the specified {@link NodeList}.
* The returned {@link Iterator} can be used for a single iteration.
*
* @param nodeList the node list to use, may not be null
* @return a new, single use {@link Iterator}
* @throws NullPointerException if nodeList is null
* @since 4.0
*/
public static NodeListIterator nodeListIterator(final NodeList nodeList) {
if (nodeList == null) {
throw new NullPointerException("NodeList must not be null");
}
return new NodeListIterator(nodeList);
}
/**
* Gets an {@link Iterator} that wraps the specified node's childNodes.
* The returned {@link Iterator} can be used for a single iteration.
* <p>
* Convenience method, allows easy iteration over NodeLists:
* <pre>
* Iterator<Node> iterator = IteratorUtils.nodeListIterator(node);
* for(Node childNode : IteratorUtils.asIterable(iterator)) {
* ...
* }
* </pre>
*
* @param node the node to use, may not be null
* @return a new, single use {@link Iterator}
* @throws NullPointerException if node is null
* @since 4.0
*/
public static NodeListIterator nodeListIterator(final Node node) {
if (node == null) {
throw new NullPointerException("Node must not be null");
}
return new NodeListIterator(node);
}
// Peeking
//-----------------------------------------------------------------------
/**
* Gets an iterator that supports one-element lookahead.
*
* @param <E> the element type
* @param iterator the iterator to decorate, not null
* @return a peeking iterator
* @throws NullPointerException if the iterator is null
* @since 4.0
*/
public static <E> Iterator<E> peekingIterator(final Iterator<? extends E> iterator) {
return PeekingIterator.peekingIterator(iterator);
}
// Pushback
//-----------------------------------------------------------------------
/**
* Gets an iterator that supports pushback of elements.
*
* @param <E> the element type
* @param iterator the iterator to decorate, not null
* @return a pushback iterator
* @throws NullPointerException if the iterator is null
* @since 4.0
*/
public static <E> Iterator<E> pushbackIterator(final Iterator<? extends E> iterator) {
return PushbackIterator.pushbackIterator(iterator);
}
// Skipping
//-----------------------------------------------------------------------
/**
* Decorates the specified iterator to skip the first N elements.
*
* @param <E> the element type
* @param iterator the iterator to decorate
* @param offset the first number of elements to skip
* @return a new skipping iterator
* @throws NullPointerException if the iterator is null
* @throws IllegalArgumentException if offset is negative
* @since 4.1
*/
public static <E> SkippingIterator<E> skippingIterator(final Iterator<E> iterator, long offset) {
return new SkippingIterator<E>(iterator, offset);
}
// Zipping
//-----------------------------------------------------------------------
/**
* Returns an iterator that interleaves elements from the decorated iterators.
*
* @param <E> the element type
* @param a the first iterator to interleave
* @param b the second iterator to interleave
* @return an iterator, interleaving the decorated iterators
* @throws NullPointerException if any iterator is null
* @since 4.1
*/
public static <E> ZippingIterator<E> zippingIterator(final Iterator<? extends E> a,
final Iterator<? extends E> b) {
return new ZippingIterator<E>(a, b);
}
/**
* Returns an iterator that interleaves elements from the decorated iterators.
*
* @param <E> the element type
* @param a the first iterator to interleave
* @param b the second iterator to interleave
* @param c the third iterator to interleave
* @return an iterator, interleaving the decorated iterators
* @throws NullPointerException if any iterator is null
* @since 4.1
*/
public static <E> ZippingIterator<E> zippingIterator(final Iterator<? extends E> a,
final Iterator<? extends E> b,
final Iterator<? extends E> c) {
return new ZippingIterator<E>(a, b, c);
}
/**
* Returns an iterator that interleaves elements from the decorated iterators.
*
* @param <E> the element type
* @param iterators the array of iterators to interleave
* @return an iterator, interleaving the decorated iterators
* @throws NullPointerException if any iterator is null
* @since 4.1
*/
public static <E> ZippingIterator<E> zippingIterator(final Iterator<? extends E>... iterators) {
return new ZippingIterator<E>(iterators);
}
// Views
//-----------------------------------------------------------------------
/**
* Gets an iterator that provides an iterator view of the given enumeration.
*
* @param <E> the element type
* @param enumeration the enumeration to use, may not be null
* @return a new iterator
* @throws NullPointerException if enumeration is null
*/
public static <E> Iterator<E> asIterator(final Enumeration<? extends E> enumeration) {
if (enumeration == null) {
throw new NullPointerException("Enumeration must not be null");
}
return new EnumerationIterator<E>(enumeration);
}
/**
* Gets an iterator that provides an iterator view of the given enumeration
* that will remove elements from the specified collection.
*
* @param <E> the element type
* @param enumeration the enumeration to use, may not be null
* @param removeCollection the collection to remove elements from, may not be null
* @return a new iterator
* @throws NullPointerException if enumeration or removeCollection is null
*/
public static <E> Iterator<E> asIterator(final Enumeration<? extends E> enumeration,
final Collection<? super E> removeCollection) {
if (enumeration == null) {
throw new NullPointerException("Enumeration must not be null");
}
if (removeCollection == null) {
throw new NullPointerException("Collection must not be null");
}
return new EnumerationIterator<E>(enumeration, removeCollection);
}
/**
* Gets an enumeration that wraps an iterator.
*
* @param <E> the element type
* @param iterator the iterator to use, may not be null
* @return a new enumeration
* @throws NullPointerException if iterator is null
*/
public static <E> Enumeration<E> asEnumeration(final Iterator<? extends E> iterator) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
return new IteratorEnumeration<E>(iterator);
}
/**
* Gets an {@link Iterable} that wraps an iterator. The returned {@link Iterable} can be
* used for a single iteration.
*
* @param <E> the element type
* @param iterator the iterator to use, may not be null
* @return a new, single use {@link Iterable}
* @throws NullPointerException if iterator is null
*/
public static <E> Iterable<E> asIterable(final Iterator<? extends E> iterator) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
return new IteratorIterable<E>(iterator, false);
}
/**
* Gets an iterable that wraps an iterator. The returned iterable can be
* used for multiple iterations.
*
* @param <E> the element type
* @param iterator the iterator to use, may not be null
* @return a new, multiple use iterable
* @throws NullPointerException if iterator is null
*/
public static <E> Iterable<E> asMultipleUseIterable(final Iterator<? extends E> iterator) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
return new IteratorIterable<E>(iterator, true);
}
/**
* Gets a list iterator based on a simple iterator.
* <p>
* As the wrapped Iterator is traversed, a LinkedList of its values is
* cached, permitting all required operations of ListIterator.
*
* @param <E> the element type
* @param iterator the iterator to use, may not be null
* @return a new iterator
* @throws NullPointerException if iterator parameter is null
*/
public static <E> ListIterator<E> toListIterator(final Iterator<? extends E> iterator) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
return new ListIteratorWrapper<E>(iterator);
}
/**
* Gets an array based on an iterator.
* <p>
* As the wrapped Iterator is traversed, an ArrayList of its values is
* created. At the end, this is converted to an array.
*
* @param iterator the iterator to use, not null
* @return an array of the iterator contents
* @throws NullPointerException if iterator parameter is null
*/
public static Object[] toArray(final Iterator<?> iterator) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
final List<?> list = toList(iterator, 100);
return list.toArray();
}
/**
* Gets an array based on an iterator.
* <p>
* As the wrapped Iterator is traversed, an ArrayList of its values is
* created. At the end, this is converted to an array.
*
* @param <E> the element type
* @param iterator the iterator to use, not null
* @param arrayClass the class of array to create
* @return an array of the iterator contents
* @throws NullPointerException if iterator parameter or arrayClass is null
* @throws ArrayStoreException if the arrayClass is invalid
*/
public static <E> E[] toArray(final Iterator<? extends E> iterator, final Class<E> arrayClass) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
if (arrayClass == null) {
throw new NullPointerException("Array class must not be null");
}
final List<E> list = toList(iterator, 100);
@SuppressWarnings("unchecked")
final E[] array = (E[]) Array.newInstance(arrayClass, list.size());
return list.toArray(array);
}
/**
* Gets a list based on an iterator.
* <p>
* As the wrapped Iterator is traversed, an ArrayList of its values is
* created. At the end, the list is returned.
*
* @param <E> the element type
* @param iterator the iterator to use, not null
* @return a list of the iterator contents
* @throws NullPointerException if iterator parameter is null
*/
public static <E> List<E> toList(final Iterator<? extends E> iterator) {
return toList(iterator, 10);
}
/**
* Gets a list based on an iterator.
* <p>
* As the wrapped Iterator is traversed, an ArrayList of its values is
* created. At the end, the list is returned.
*
* @param <E> the element type
* @param iterator the iterator to use, not null
* @param estimatedSize the initial size of the ArrayList
* @return a list of the iterator contents
* @throws NullPointerException if iterator parameter is null
* @throws IllegalArgumentException if the size is less than 1
*/
public static <E> List<E> toList(final Iterator<? extends E> iterator, final int estimatedSize) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
if (estimatedSize < 1) {
throw new IllegalArgumentException("Estimated size must be greater than 0");
}
final List<E> list = new ArrayList<E>(estimatedSize);
while (iterator.hasNext()) {
list.add(iterator.next());
}
return list;
}
/**
* Gets a suitable Iterator for the given object.
* <p>
* This method can handle objects as follows
* <ul>
* <li>null - empty iterator
* <li>Iterator - returned directly
* <li>Enumeration - wrapped
* <li>Collection - iterator from collection returned
* <li>Map - values iterator returned
* <li>Dictionary - values (elements) enumeration returned as iterator
* <li>array - iterator over array returned
* <li>object with iterator() public method accessed by reflection
* <li>object - singleton iterator
* <li>NodeList - iterator over the list
* <li>Node - iterator over the child nodes
* </ul>
*
* @param obj the object to convert to an iterator
* @return a suitable iterator, never null
*/
public static Iterator<?> getIterator(final Object obj) {
if (obj == null) {
return emptyIterator();
}
if (obj instanceof Iterator) {
return (Iterator<?>) obj;
}
if (obj instanceof Iterable) {
return ((Iterable<?>) obj).iterator();
}
if (obj instanceof Object[]) {
return new ObjectArrayIterator<Object>((Object[]) obj);
}
if (obj instanceof Enumeration) {
return new EnumerationIterator<Object>((Enumeration<?>) obj);
}
if (obj instanceof Map) {
return ((Map<?, ?>) obj).values().iterator();
}
if (obj instanceof NodeList) {
return new NodeListIterator((NodeList) obj);
}
if (obj instanceof Node) {
return new NodeListIterator((Node) obj);
}
if (obj instanceof Dictionary) {
return new EnumerationIterator<Object>(((Dictionary<?, ?>) obj).elements());
} else if (obj.getClass().isArray()) {
return new ArrayIterator<Object>(obj);
}
try {
final Method method = obj.getClass().getMethod("iterator", (Class[]) null);
if (Iterator.class.isAssignableFrom(method.getReturnType())) {
final Iterator<?> it = (Iterator<?>) method.invoke(obj, (Object[]) null);
if (it != null) {
return it;
}
}
} catch (final RuntimeException e) { // NOPMD
// ignore
} catch (final NoSuchMethodException e) { // NOPMD
// ignore
} catch (final IllegalAccessException e) { // NOPMD
// ignore
} catch (final InvocationTargetException e) { // NOPMD
// ignore
}
return singletonIterator(obj);
}
// Utility methods
//-----------------------------------------------------------------------
/**
* Applies the closure to each element of the provided iterator.
*
* @param <E> the element type
* @param iterator the iterator to use, may be null
* @param closure the closure to apply to each element, may not be null
* @throws NullPointerException if closure is null
* @since 4.1
*/
public static <E> void forEach(final Iterator<E> iterator, final Closure<? super E> closure) {
if (closure == null) {
throw new NullPointerException("Closure must not be null");
}
if (iterator != null) {
while (iterator.hasNext()) {
final E element = iterator.next();
closure.execute(element);
}
}
}
/**
* Executes the given closure on each but the last element in the iterator.
* <p>
* If the input iterator is null no change is made.
*
* @param <E> the type of object the {@link Iterator} contains
* @param iterator the iterator to get the input from, may be null
* @param closure the closure to perform, may not be null
* @return the last element in the iterator, or null if iterator is null or empty
* @throws NullPointerException if closure is null
* @since 4.1
*/
public static <E> E forEachButLast(final Iterator<E> iterator, final Closure<? super E> closure) {
if (closure == null) {
throw new NullPointerException("Closure must not be null.");
}
if (iterator != null) {
while (iterator.hasNext()) {
final E element = iterator.next();
if (iterator.hasNext()) {
closure.execute(element);
} else {
return element;
}
}
}
return null;
}
/**
* Finds the first element in the given iterator which matches the given predicate.
* <p>
* A <code>null</code> or empty iterator returns null.
*
* @param <E> the element type
* @param iterator the iterator to search, may be null
* @param predicate the predicate to use, may not be null
* @return the first element of the iterator which matches the predicate or null if none could be found
* @throws NullPointerException if predicate is null
* @since 4.1
*/
public static <E> E find(final Iterator<E> iterator, final Predicate<? super E> predicate) {
if (predicate == null) {
throw new NullPointerException("Predicate must not be null");
}
if (iterator != null) {
while (iterator.hasNext()) {
final E element = iterator.next();
if (predicate.evaluate(element)) {
return element;
}
}
}
return null;
}
/**
* Returns the index of the first element in the specified iterator that
* matches the given predicate.
* <p>
* A <code>null</code> or empty iterator returns -1.
*
* @param <E> the element type
* @param iterator the iterator to search, may be null
* @param predicate the predicate to use, may not be null
* @return the index of the first element which matches the predicate or -1 if none matches
* @throws NullPointerException if predicate is null
* @since 4.1
*/
public static <E> int indexOf(final Iterator<E> iterator, final Predicate<? super E> predicate) {
if (predicate == null) {
throw new NullPointerException("Predicate must not be null");
}
if (iterator != null) {
for(int index = 0; iterator.hasNext(); index++) {
final E element = iterator.next();
if (predicate.evaluate(element)) {
return index;
}
}
}
return -1;
}
/**
* Answers true if a predicate is true for any element of the iterator.
* <p>
* A <code>null</code> or empty iterator returns false.
*
* @param <E> the type of object the {@link Iterator} contains
* @param iterator the {@link Iterator} to use, may be null
* @param predicate the predicate to use, may not be null
* @return true if any element of the collection matches the predicate, false otherwise
* @throws NullPointerException if predicate is null
* @since 4.1
*/
public static <E> boolean matchesAny(final Iterator<E> iterator, final Predicate<? super E> predicate) {
return indexOf(iterator, predicate) != -1;
}
/**
* Answers true if a predicate is true for every element of an iterator.
* <p>
* A <code>null</code> or empty iterator returns true.
*
* @param <E> the type of object the {@link Iterator} contains
* @param iterator the {@link Iterator} to use, may be null
* @param predicate the predicate to use, may not be null
* @return true if every element of the collection matches the predicate or if the
* collection is empty, false otherwise
* @throws NullPointerException if predicate is null
* @since 4.1
*/
public static <E> boolean matchesAll(final Iterator<E> iterator, final Predicate<? super E> predicate) {
if (predicate == null) {
throw new NullPointerException("Predicate must not be null");
}
if (iterator != null) {
while (iterator.hasNext()) {
final E element = iterator.next();
if (!predicate.evaluate(element)) {
return false;
}
}
}
return true;
}
/**
* Checks if the given iterator is empty.
* <p>
* A <code>null</code> or empty iterator returns true.
*
* @param iterator the {@link Iterator} to use, may be null
* @return true if the iterator is exhausted or null, false otherwise
* @since 4.1
*/
public static boolean isEmpty(final Iterator<?> iterator) {
return iterator == null || !iterator.hasNext();
}
/**
* Checks if the object is contained in the given iterator.
* <p>
* A <code>null</code> or empty iterator returns false.
*
* @param <E> the type of object the {@link Iterator} contains
* @param iterator the iterator to check, may be null
* @param object the object to check
* @return true if the object is contained in the iterator, false otherwise
* @since 4.1
*/
public static <E> boolean contains(final Iterator<E> iterator, final Object object) {
return matchesAny(iterator, EqualPredicate.equalPredicate(object));
}
/**
* Returns the <code>index</code>-th value in {@link Iterator}, throwing
* <code>IndexOutOfBoundsException</code> if there is no such element.
* <p>
* The Iterator is advanced to <code>index</code> (or to the end, if
* <code>index</code> exceeds the number of entries) as a side effect of this method.
*
* @param <E> the type of object in the {@link Iterator}
* @param iterator the iterator to get a value from
* @param index the index to get
* @return the object at the specified index
* @throws IndexOutOfBoundsException if the index is invalid
* @since 4.1
*/
public static <E> E get(final Iterator<E> iterator, final int index) {
int i = index;
CollectionUtils.checkIndexBounds(i);
while (iterator.hasNext()) {
i--;
if (i == -1) {
return iterator.next();
}
iterator.next();
}
throw new IndexOutOfBoundsException("Entry does not exist: " + i);
}
/**
* Returns the number of elements contained in the given iterator.
* <p>
* A <code>null</code> or empty iterator returns {@code 0}.
*
* @param iterator the iterator to check, may be null
* @return the number of elements contained in the iterator
* @since 4.1
*/
public static int size(final Iterator<?> iterator) {
int size = 0;
if (iterator != null) {
while (iterator.hasNext()) {
iterator.next();
size++;
}
}
return size;
}
/**
* Returns a string representation of the elements of the specified iterator.
* <p>
* The string representation consists of a list of the iterator's elements,
* enclosed in square brackets ({@code "[]"}). Adjacent elements are separated
* by the characters {@code ", "} (a comma followed by a space). Elements are
* converted to strings as by {@code String.valueOf(Object)}.
*
* @param <E> the element type
* @param iterator the iterator to convert to a string, may be null
* @return a string representation of {@code iterator}
* @since 4.1
*/
public static <E> String toString(final Iterator<E> iterator) {
return toString(iterator, TransformerUtils.stringValueTransformer(),
DEFAULT_TOSTRING_DELIMITER, DEFAULT_TOSTRING_PREFIX,
DEFAULT_TOSTRING_SUFFIX);
}
/**
* Returns a string representation of the elements of the specified iterator.
* <p>
* The string representation consists of a list of the iterable's elements,
* enclosed in square brackets ({@code "[]"}). Adjacent elements are separated
* by the characters {@code ", "} (a comma followed by a space). Elements are
* converted to strings as by using the provided {@code transformer}.
*
* @param <E> the element type
* @param iterator the iterator to convert to a string, may be null
* @param transformer the transformer used to get a string representation of an element
* @return a string representation of {@code iterator}
* @throws NullPointerException if {@code transformer} is null
* @since 4.1
*/
public static <E> String toString(final Iterator<E> iterator,
final Transformer<? super E, String> transformer) {
return toString(iterator, transformer, DEFAULT_TOSTRING_DELIMITER,
DEFAULT_TOSTRING_PREFIX, DEFAULT_TOSTRING_SUFFIX);
}
/**
* Returns a string representation of the elements of the specified iterator.
* <p>
* The string representation consists of a list of the iterator's elements,
* enclosed by the provided {@code prefix} and {@code suffix}. Adjacent elements
* are separated by the provided {@code delimiter}. Elements are converted to
* strings as by using the provided {@code transformer}.
*
* @param <E> the element type
* @param iterator the iterator to convert to a string, may be null
* @param transformer the transformer used to get a string representation of an element
* @param delimiter the string to delimit elements
* @param prefix the prefix, prepended to the string representation
* @param suffix the suffix, appended to the string representation
* @return a string representation of {@code iterator}
* @throws NullPointerException if either transformer, delimiter, prefix or suffix is null
* @since 4.1
*/
public static <E> String toString(final Iterator<E> iterator,
final Transformer<? super E, String> transformer,
final String delimiter,
final String prefix,
final String suffix) {
if (transformer == null) {
throw new NullPointerException("transformer may not be null");
}
if (delimiter == null) {
throw new NullPointerException("delimiter may not be null");
}
if (prefix == null) {
throw new NullPointerException("prefix may not be null");
}
if (suffix == null) {
throw new NullPointerException("suffix may not be null");
}
final StringBuilder stringBuilder = new StringBuilder(prefix);
if (iterator != null) {
while (iterator.hasNext()) {
final E element = iterator.next();
stringBuilder.append(transformer.transform(element));
stringBuilder.append(delimiter);
}
if(stringBuilder.length() > prefix.length()) {
stringBuilder.setLength(stringBuilder.length() - delimiter.length());
}
}
stringBuilder.append(suffix);
return stringBuilder.toString();
}
}