    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.collections4;
    018
    019import java.util.ArrayList;
    020import java.util.Enumeration;
    021import java.util.List;
    022import java.util.Set;
    023import java.util.StringTokenizer;
    024
    025import org.apache.commons.collections4.iterators.EnumerationIterator;
    026import org.apache.commons.collections4.iterators.IteratorIterable;
    027
    028/**
    029 * Provides utility methods for {@link Enumeration} instances.
    030 *
    031 * @since 3.0
    032 */
    033public class EnumerationUtils {
    034
    035    /**
    036     * Creates an {@link Iterable} that wraps an {@link Enumeration}. The returned {@link Iterable} can be used for a
    037     * single iteration.
    038     *
    039     * @param <T> the element type
    040     * @param enumeration the enumeration to use, may not be null
    041     * @return a new, single use {@link Iterable}
    042     * @since 4.5.0-M1
    043     */
    044    public static <T> Iterable<T> asIterable(final Enumeration<T> enumeration) {
    045        return new IteratorIterable<>(new EnumerationIterator<>(enumeration));
    046    }
    047
    048    /**
    049     * Gets the {@code index}-th value in the {@link Enumeration}, throwing
    050     * {@code IndexOutOfBoundsException} if there is no such element.
    051     * <p>
    052     * The Enumeration is advanced to {@code index} (or to the end, if
    053     * {@code index} exceeds the number of entries) as a side effect of this method.
    054     * </p>
    055     *
    056     * @param e  the enumeration to get a value from
    057     * @param index  the index to get
    058     * @param <T> the type of object in the {@link Enumeration}
    059     * @return the object at the specified index
    060     * @throws IndexOutOfBoundsException if the index is invalid
    061     * @throws IllegalArgumentException if the object type is invalid
    062     * @since 4.1
    063     */
    064    public static <T> T get(final Enumeration<T> e, final int index) {
    065        CollectionUtils.checkIndexBounds(index);
    066        int i = index;
    067        while (e.hasMoreElements()) {
    068            i--;
    069            if (i == -1) {
    070                return e.nextElement();
    071            }
    072            e.nextElement();
    073        }
    074        throw new IndexOutOfBoundsException("Entry does not exist: " + i);
    075    }
    076
    077    /**
    078     * Creates a list based on an enumeration.
    079     *
    080     * <p>As the enumeration is traversed, an ArrayList of its values is
    081     * created. The new list is returned.</p>
    082     *
    083     * @param <E> the element type
    084     * @param enumeration  the enumeration to traverse, which should not be {@code null}.
    085     * @return a list containing all elements of the given enumeration
    086     * @throws NullPointerException if the enumeration parameter is {@code null}.
    087     */
    088    public static <E> List<E> toList(final Enumeration<? extends E> enumeration) {
    089        return IteratorUtils.toList(new EnumerationIterator<>(enumeration));
    090    }
    091
    092    /**
    093     * Override toList(Enumeration) for StringTokenizer as it implements Enumeration&lt;Object&gt;
    094     * for the sake of backward compatibility.
    095     *
    096     * @param stringTokenizer  the tokenizer to convert to a {@link List}&lt;{@link String}&gt;
    097     * @return a list containing all tokens of the given StringTokenizer
    098     */
    099    public static List<String> toList(final StringTokenizer stringTokenizer) {
    100        final List<String> result = new ArrayList<>(stringTokenizer.countTokens());
    101        while (stringTokenizer.hasMoreTokens()) {
    102            result.add(stringTokenizer.nextToken());
    103        }
    104        return result;
    105    }
    106
    107    /**
    108     * Creates a set based on an enumeration.
    109     *
    110     * <p>As the enumeration is traversed, an HashSet of its values is
    111     * created. The new set is returned.</p>
    112     *
    113     * @param <E> the element type
    114     * @param enumeration  the enumeration to traverse, which should not be {@code null}.
    115     * @return a set containing all elements of the given enumeration.
    116     * @throws NullPointerException if the enumeration parameter is {@code null}.
    117     * @since 4.5.0-M4
    118     */
    119    public static <E> Set<E> toSet(final Enumeration<? extends E> enumeration) {
    120        return IteratorUtils.toSet(new EnumerationIterator<>(enumeration));
    121    }
    122
    123    /**
    124     * Don't allow instances.
    125     */
    126    private EnumerationUtils() {
    127        // no instances.
    128    }
    129
    130}