package com.wrox.algorithms.iteration;/** * An {@link Iterator} over the contents of an array. * */public class ArrayIterator implements Iterator {    /** The array to iterator over. */    private final Object[] _array;    /** The position(0, 1, 2...) of the first element. */    private final int _first;    /* The position (0, 1, 2...) of the last element. */    private final int _last;    /** The position (0, 1, 2...) of the current element in the array. */    private int _current = -1;    /**     * Constructor.     *     * @param array The array to iterate over.     */    public ArrayIterator(Object[] array) {        assert array != null : "array can't be null";        _array = array;        _first = 0;        _last = array.length - 1;    }    /**     * Constructor.     *     * @param array The array to iterator over.     * @param start The position (0, 1, 2...) of the element from which to begin iterating.     * @param length The number of elements to iterator over.     */    public ArrayIterator(Object[] array, int start, int length) {        assert array != null : "array can't be null";        assert start >= 0 : "start can't be < 0";        assert start < array.length : "start can't be > array.length";        assert length >= 0 : "length can't be < 0";        _array = array;        _first = start;        _last = start + length - 1;        assert _last < array.length : "start + length can't be > array.length";    }    public void first() {        _current = _first;    }    public void last() {        _current = _last;    }    public boolean isDone() {        return _current < _first || _current > _last;    }    public void next() {        ++_current;    }    public void previous() {        --_current;    }    public Object current() throws IteratorOutOfBoundsException {        if (isDone()) {            throw new IteratorOutOfBoundsException();        }        return _array[_current];    }}