Java tutorial
// GenericsNote: Converted, although unsatisfying because there does not seem to be a way to generify the primitive types. /* * Copyright 1999-2004 The Apache Software Foundation * * Licensed 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.collections15.iterators; import org.apache.commons.collections15.ResettableIterator; import java.lang.reflect.Array; import java.util.NoSuchElementException; /** * 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.collections15.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. * * @author James Strachan * @author Mauricio S. Moura * @author Michael A. Smith * @author Neil O'Toole * @author Matt Hall, John Watkinson, Stephen Colebourne * @version $Revision: 1.1 $ $Date: 2005/10/11 17:05:24 $ * @since Commons Collections 1.0 */ public class ArrayIterator<E> implements ResettableIterator<E> { /** * The array to iterate over */ protected Object array; /** * The start index to loop from */ protected int startIndex = 0; /** * The end index to loop to */ protected int endIndex = 0; /** * The current iterator index */ protected int index = 0; // Constructors // ---------------------------------------------------------------------- /** * 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. * * @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. * * @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. * * @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. * * @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. * * @return true if there is a next element to return */ public boolean hasNext() { return (index < endIndex); } /** * 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 E next() { if (hasNext() == false) { throw new NoSuchElementException(); } return (E) Array.get(array, index++); } /** * 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. * * @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. * <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. */ public void reset() { this.index = this.startIndex; } }