001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
003// * distributed with this work for additional information regarding copyright ownership.  The ASF licenses this file        *
004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
005// * with the License.  You may obtain a copy of the License at                                                              *
006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
009// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an  *
010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the        *
011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.internal;
014
015import java.util.*;
016
017/**
018 * Implements a reversed iteration {@link Iterable} without altering the underlying list.
019 *
020 * @param <T> The entry type.
021 */
022public class ReverseIterable<T> implements Iterable<T> {
023    private final List<T> list;
024
025    /**
026     * Constructor
027     *
028     * @param list The original list.
029     */
030    public ReverseIterable(List<T> list) {
031        this.list = list;
032    }
033
034    /**
035     * Convenience method for constructing instances.
036     *
037     * @param list The original list.
038     * @return A new {@link ReverseIterable}.
039     */
040    public static <T> ReverseIterable<T> of(List<T> list) {
041        return new ReverseIterable<>(list);
042    }
043
044    /**
045     * Convenience method for constructing instances.
046     *
047     * @param list The original list.
048     * @return A new {@link ReverseIterable}.
049     */
050    public static <T> ReverseIterable<T> of(T[] list) {
051        return new ReverseIterable<>(Arrays.asList(list));
052    }
053
054    @Override
055   public Iterator<T> iterator() {
056        final ListIterator<T> i = list.listIterator(list.size());
057
058        return new Iterator<T>() {
059            @Override
060         public boolean hasNext() { return i.hasPrevious(); }
061            @Override
062         public T next() { return i.previous(); }
063            @Override
064         public void remove() { i.remove(); }
065        };
066    }
067}