    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.iterators;
    018
    019import java.lang.reflect.Array;
    020import java.util.NoSuchElementException;
    021
    022import org.apache.commons.collections4.ResettableIterator;
    023
    024/**
    025 * Implements an {@link java.util.Iterator Iterator} over any array.
    026 * <p>
    027 * The array can be either an array of object or of primitives. If you know
    028 * that you have an object array, the
    029 * {@link org.apache.commons.collections4.iterators.ObjectArrayIterator ObjectArrayIterator}
    030 * class is a better choice, as it will perform better.
    031 * </p>
    032 * <p>
    033 * The iterator implements a {@link #reset} method, allowing the reset of
    034 * the iterator back to the start if required.
    035 * </p>
    036 *
    037 * @param <E> the type of elements returned by this iterator.
    038 * @since 1.0
    039 */
    040public class ArrayIterator<E> implements ResettableIterator<E> {
    041
    042    /** The array to iterate over */
    043    final Object array;
    044    /** The start index to loop from */
    045    final int startIndex;
    046    /** The end index to loop to */
    047    final int endIndex;
    048    /** The current iterator index */
    049    int index;
    050
    051    /**
    052     * Constructs an ArrayIterator that will iterate over the values in the
    053     * specified array.
    054     *
    055     * @param array the array to iterate over.
    056     * @throws IllegalArgumentException if {@code array} is not an array.
    057     * @throws NullPointerException if {@code array} is {@code null}
    058     */
    059    public ArrayIterator(final Object array) {
    060        this(array, 0);
    061    }
    062
    063    /**
    064     * Constructs an ArrayIterator that will iterate over the values in the
    065     * specified array from a specific start index.
    066     *
    067     * @param array  the array to iterate over.
    068     * @param startIndex  the index to start iterating at.
    069     * @throws IllegalArgumentException if {@code array} is not an array.
    070     * @throws NullPointerException if {@code array} is {@code null}
    071     * @throws IndexOutOfBoundsException if the index is invalid
    072     */
    073    public ArrayIterator(final Object array, final int startIndex) {
    074        this(array, startIndex, Array.getLength(array));
    075    }
    076
    077    /**
    078     * Constructs an ArrayIterator that will iterate over a range of values
    079     * in the specified array.
    080     *
    081     * @param array  the array to iterate over.
    082     * @param startIndex  the index to start iterating at.
    083     * @param endIndex  the index to finish iterating at.
    084     * @throws IllegalArgumentException if {@code array} is not an array.
    085     * @throws NullPointerException if {@code array} is {@code null}
    086     * @throws IndexOutOfBoundsException if either index is invalid
    087     */
    088    public ArrayIterator(final Object array, final int startIndex, final int endIndex) {
    089        this.array = array;
    090        this.startIndex = startIndex;
    091        this.endIndex = endIndex;
    092        this.index = startIndex;
    093
    094        final int len = Array.getLength(array);
    095        checkBound(startIndex, len, "start");
    096        checkBound(endIndex, len, "end");
    097        if (endIndex < startIndex) {
    098            throw new IllegalArgumentException("End index must not be less than start index.");
    099        }
    100    }
    101
    102    /**
    103     * Checks whether the index is valid or not.
    104     *
    105     * @param bound  the index to check
    106     * @param len  the length of the array
    107     * @param type  the index type (for error messages)
    108     * @throws IndexOutOfBoundsException if the index is invalid
    109     */
    110    protected void checkBound(final int bound, final int len, final String type) {
    111        if (bound > len) {
    112            throw new ArrayIndexOutOfBoundsException("Attempt to make an ArrayIterator that " + type + "s beyond the end of the array. ");
    113        }
    114        if (bound < 0) {
    115            throw new ArrayIndexOutOfBoundsException("Attempt to make an ArrayIterator that " + type + "s before the start of the array. ");
    116        }
    117    }
    118
    119    /**
    120     * Gets the array that this iterator is iterating over.
    121     *
    122     * @return the array this iterator iterates over.
    123     */
    124    public Object getArray() {
    125        return array;
    126    }
    127
    128    /**
    129     * Gets the end index to loop to.
    130     *
    131     * @return the end index
    132     * @since 4.0
    133     */
    134    public int getEndIndex() {
    135        return endIndex;
    136    }
    137
    138    /**
    139     * Gets the start index to loop from.
    140     *
    141     * @return the start index
    142     * @since 4.0
    143     */
    144    public int getStartIndex() {
    145        return startIndex;
    146    }
    147
    148    /**
    149     * Returns true if there are more elements to return from the array.
    150     *
    151     * @return true if there is a next element to return
    152     */
    153    @Override
    154    public boolean hasNext() {
    155        return index < endIndex;
    156    }
    157
    158    /**
    159     * Returns the next element in the array.
    160     *
    161     * @return the next element in the array
    162     * @throws NoSuchElementException if all the elements in the array
    163     *  have already been returned
    164     */
    165    @Override
    166    @SuppressWarnings("unchecked")
    167    public E next() {
    168        if (!hasNext()) {
    169            throw new NoSuchElementException();
    170        }
    171        return (E) Array.get(array, index++);
    172    }
    173
    174    /**
    175     * Throws {@link UnsupportedOperationException}.
    176     *
    177     * @throws UnsupportedOperationException always
    178     */
    179    @Override
    180    public void remove() {
    181        throw new UnsupportedOperationException("remove() method is not supported");
    182    }
    183
    184    /**
    185     * Resets the iterator back to the start index.
    186     */
    187    @Override
    188    public void reset() {
    189        index = startIndex;
    190    }
    191
    192}