/*
 *  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.collections.iterators;

import java.lang.reflect.Array;
import java.util.NoSuchElementException;

import org.apache.commons.collections.ResettableIterator;

Implements an Iterator over any array. 
 The array can be either an array of object or of primitives. If you know that you have an object array, the ObjectArrayIterator class is a better choice, as it will perform better. 
 The iterator implements a reset method, allowing the reset of the iterator back to the start if required. 
Author:
James Strachan, Mauricio S. Moura, Michael A. Smith, Neil O'Toole, Stephen Colebourne
Since:
Commons Collections 1.0
Version:
$Revision: 647116 $ $Date: 2008-04-11 13:23:08 +0200 (Fri, 11 Apr 2008) $/** 
 * Implements an {@link java.util.Iterator Iterator} over any array.
 * <p>
 * The array can be either an array of object or of primitives. If you know 
 * that you have an object array, the 
 * {@link org.apache.commons.collections.iterators.ObjectArrayIterator ObjectArrayIterator}
 * class is a better choice, as it will perform better.
 * <p>
 * The iterator implements a {@link #reset} method, allowing the reset of 
 * the iterator back to the start if required.
 *
 * @since Commons Collections 1.0
 * @version $Revision: 647116 $ $Date: 2008-04-11 13:23:08 +0200 (Fri, 11 Apr 2008) $
 *
 * @author James Strachan
 * @author Mauricio S. Moura
 * @author Michael A. Smith
 * @author Neil O'Toole
 * @author Stephen Colebourne
 */
public class ArrayIterator implements ResettableIterator {

    
The array to iterate over /** The array to iterate over */    
    protected Object array;
    
The start index to loop from /** The start index to loop from */
    protected int startIndex = 0;
    
The end index to loop to /** The end index to loop to */
    protected int endIndex = 0;
    
The current iterator index /** The current iterator index */
    protected int index = 0;
    
    // Constructors
    // ----------------------------------------------------------------------
    
Constructor for use with setArray.
 Using this constructor, the iterator is equivalent to an empty iterator until setArray(Object) is called to establish the array to iterate over. /**
     * Constructor for use with <code>setArray</code>.
     * <p>
     * Using this constructor, the iterator is equivalent to an empty iterator
     * until {@link #setArray(Object)} is  called to establish the array to iterate over.
     */
    public ArrayIterator() {
        super();
    }
   
    
Constructs an ArrayIterator that will iterate over the values in the
specified array.
Params:
array – the array to iterate over.
Throws:
IllegalArgumentException – if array is not an array.
NullPointerException – if array is null/**
     * Constructs an ArrayIterator that will iterate over the values in the
     * specified array.
     *
     * @param array the array to iterate over.
     * @throws IllegalArgumentException if <code>array</code> is not an array.
     * @throws NullPointerException if <code>array</code> is <code>null</code>
     */
    public ArrayIterator(final Object array) {
        super();
        setArray(array);
    }

    
Constructs an ArrayIterator that will iterate over the values in the
specified array from a specific start index.
Params:
array –  the array to iterate over.
startIndex –  the index to start iterating at.
Throws:
IllegalArgumentException – if array is not an array.
NullPointerException – if array is null
IndexOutOfBoundsException – if the index is invalid/**
     * Constructs an ArrayIterator that will iterate over the values in the
     * specified array from a specific start index.
     *
     * @param array  the array to iterate over.
     * @param startIndex  the index to start iterating at.
     * @throws IllegalArgumentException if <code>array</code> is not an array.
     * @throws NullPointerException if <code>array</code> is <code>null</code>
     * @throws IndexOutOfBoundsException if the index is invalid
     */
    public ArrayIterator(final Object array, final int startIndex) {
        super();
        setArray(array);
        checkBound(startIndex, "start");
        this.startIndex = startIndex;
        this.index = startIndex;
    }

    
Construct an ArrayIterator that will iterate over a range of values 
in the specified array.
Params:
array –  the array to iterate over.
startIndex –  the index to start iterating at.
endIndex –  the index to finish iterating at.
Throws:
IllegalArgumentException – if array is not an array.
NullPointerException – if array is null
IndexOutOfBoundsException – if either index is invalid/**
     * Construct an ArrayIterator that will iterate over a range of values 
     * in the specified array.
     *
     * @param array  the array to iterate over.
     * @param startIndex  the index to start iterating at.
     * @param endIndex  the index to finish iterating at.
     * @throws IllegalArgumentException if <code>array</code> is not an array.
     * @throws NullPointerException if <code>array</code> is <code>null</code>
     * @throws IndexOutOfBoundsException if either index is invalid
     */
    public ArrayIterator(final Object array, final int startIndex, final int endIndex) {
        super();
        setArray(array);
        checkBound(startIndex, "start");
        checkBound(endIndex, "end");
        if (endIndex < startIndex) {
            throw new IllegalArgumentException("End index must not be less than start index.");
        }
        this.startIndex = startIndex;
        this.endIndex = endIndex;
        this.index = startIndex;
    }

    
Checks whether the index is valid or not.
Params:
bound –  the index to check
type –  the index type (for error messages)
Throws:
IndexOutOfBoundsException – if the index is invalid/**
     * Checks whether the index is valid or not.
     * 
     * @param bound  the index to check
     * @param type  the index type (for error messages)
     * @throws IndexOutOfBoundsException if the index is invalid
     */
    protected void checkBound(final int bound, final String type ) {
        if (bound > this.endIndex) {
            throw new ArrayIndexOutOfBoundsException(
              "Attempt to make an ArrayIterator that " + type +
              "s beyond the end of the array. "
            );
        }
        if (bound < 0) {
            throw new ArrayIndexOutOfBoundsException(
              "Attempt to make an ArrayIterator that " + type +
              "s before the start of the array. "
            );
        }
    }

    // Iterator interface
    //-----------------------------------------------------------------------
    
Returns true if there are more elements to return from the array.
Returns:
true if there is a next element to return/**
     * Returns true if there are more elements to return from the array.
     *
     * @return true if there is a next element to return
     */
    public boolean hasNext() {
        return (index < endIndex);
    }

    
Returns the next element in the array.
Throws:
NoSuchElementException – if all the elements in the array
 have already been returned
Returns:
the next element in the array/**
     * Returns the next element in the array.
     *
     * @return the next element in the array
     * @throws NoSuchElementException if all the elements in the array
     *  have already been returned
     */
    public Object next() {
        if (hasNext() == false) {
            throw new NoSuchElementException();
        }
        return Array.get(array, index++);
    }

    
Throws UnsupportedOperationException. 
Throws:
UnsupportedOperationException – always/**
     * Throws {@link UnsupportedOperationException}.
     *
     * @throws UnsupportedOperationException always
     */
    public void remove() {
        throw new UnsupportedOperationException("remove() method is not supported");
    }

    // Properties
    //-----------------------------------------------------------------------
    
Gets the array that this iterator is iterating over. 
Returns:
the array this iterator iterates over, or null if the no-arg constructor was used and setArray(Object) has never been called with a valid array./**
     * Gets the array that this iterator is iterating over. 
     *
     * @return the array this iterator iterates over, or <code>null</code> if
     *  the no-arg constructor was used and {@link #setArray(Object)} has never
     *  been called with a valid array.
     */
    public Object getArray() {
        return array;
    }
    
    
Sets the array that the ArrayIterator should iterate over.
 If an array has previously been set (using the single-arg constructor or this method) then that array is discarded in favour of this one. Iteration is restarted at the start of the new array. Although this can be used to reset iteration, the reset() method is a more effective choice. 
Params:
array – the array that the iterator should iterate over.
Throws:
IllegalArgumentException – if array is not an array.
NullPointerException – if array is null/**
     * Sets the array that the ArrayIterator should iterate over.
     * <p>
     * If an array has previously been set (using the single-arg constructor
     * or this method) then that array is discarded in favour of this one.
     * Iteration is restarted at the start of the new array.
     * Although this can be used to reset iteration, the {@link #reset()} method
     * is a more effective choice.
     *
     * @param array the array that the iterator should iterate over.
     * @throws IllegalArgumentException if <code>array</code> is not an array.
     * @throws NullPointerException if <code>array</code> is <code>null</code>
     */
    public void setArray(final Object array) {
        // Array.getLength throws IllegalArgumentException if the object is not
        // an array or NullPointerException if the object is null.  This call
        // is made before saving the array and resetting the index so that the
        // array iterator remains in a consistent state if the argument is not
        // an array or is null.
        this.endIndex = Array.getLength(array);
        this.startIndex = 0;
        this.array = array;
        this.index = 0;
    }
    
    
Resets the iterator back to the start index.
/**
     * Resets the iterator back to the start index.
     */
    public void reset() {
        this.index = this.startIndex;
    }

}