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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.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.StringTokenizer;
import org.apache.commons.collections4.iterators.EnumerationIterator;
import org.apache.commons.collections4.iterators.IteratorIterable;
/**
* Provides utility methods for {@link Enumeration} instances.
*
* @since 3.0
*/
public class EnumerationUtils {
/**
* EnumerationUtils is not normally instantiated.
*/
private EnumerationUtils() {
// no instances.
}
/**
* Creates an {@link Iterable} that wraps an {@link Enumeration}. The returned {@link Iterable} can be used for a
* single iteration.
*
* @param <T> the element type
* @param enumeration the enumeration to use, may not be null
* @return a new, single use {@link Iterable}
* @since 4.5
*/
public static <T> Iterable<T> asIterable(final Enumeration<T> enumeration) {
return new IteratorIterable<>(new EnumerationIterator<>(enumeration));
}
/**
* Returns the {@code index}-th value in the {@link Enumeration}, throwing
* {@code IndexOutOfBoundsException} if there is no such element.
* <p>
* The Enumeration is advanced to {@code index} (or to the end, if
* {@code index} exceeds the number of entries) as a side effect of this method.
*
* @param e the enumeration to get a value from
* @param index the index to get
* @param <T> the type of object in the {@link Enumeration}
* @return the object at the specified index
* @throws IndexOutOfBoundsException if the index is invalid
* @throws IllegalArgumentException if the object type is invalid
* @since 4.1
*/
public static <T> T get(final Enumeration<T> e, final int index) {
CollectionUtils.checkIndexBounds(index);
int i = index;
while (e.hasMoreElements()) {
i--;
if (i == -1) {
return e.nextElement();
}
e.nextElement();
}
throw new IndexOutOfBoundsException("Entry does not exist: " + i);
}
/**
* Creates a list based on an enumeration.
*
* <p>As the enumeration is traversed, an ArrayList of its values is
* created. The new list is returned.</p>
*
* @param <E> the element type
* @param enumeration the enumeration to traverse, which should not be {@code null}.
* @return a list containing all elements of the given enumeration
* @throws NullPointerException if the enumeration parameter is {@code null}.
*/
public static <E> List<E> toList(final Enumeration<? extends E> enumeration) {
return IteratorUtils.toList(new EnumerationIterator<>(enumeration));
}
/**
* Override toList(Enumeration) for StringTokenizer as it implements Enumeration&lt;Object&gt;
* for the sake of backward compatibility.
*
* @param stringTokenizer the tokenizer to convert to a {@link List}&lt;{@link String}&gt;
* @return a list containing all tokens of the given StringTokenizer
*/
public static List<String> toList(final StringTokenizer stringTokenizer) {
final List<String> result = new ArrayList<>(stringTokenizer.countTokens());
while (stringTokenizer.hasMoreTokens()) {
result.add(stringTokenizer.nextToken());
}
return result;
}
}