Java tutorial
/* * 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.collections4.iterators; import java.lang.reflect.Array; import java.util.NoSuchElementException; import org.apache.commons.collections4.ResettableIterator; /** * 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.collections4.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 1.0 * @version $Id: ArrayIterator.java 1494282 2013-06-18 20:09:15Z sebb $ */ public class ArrayIterator<E> implements ResettableIterator<E> { /** The array to iterate over */ final Object array; /** The start index to loop from */ final int startIndex; /** The end index to loop to */ final int endIndex; /** The current iterator index */ int index = 0; // Constructors // ---------------------------------------------------------------------- /** * 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) { this(array, 0); } /** * 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) { this(array, startIndex, Array.getLength(array)); } /** * 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(); this.array = array; this.startIndex = startIndex; this.endIndex = endIndex; this.index = startIndex; final int len = Array.getLength(array); checkBound(startIndex, len, "start"); checkBound(endIndex, len, "end"); if (endIndex < startIndex) { throw new IllegalArgumentException("End index must not be less than start index."); } } /** * Checks whether the index is valid or not. * * @param bound the index to check * @param len the length of the array * @param type the index type (for error messages) * @throws IndexOutOfBoundsException if the index is invalid */ protected void checkBound(final int bound, final int len, final String type) { if (bound > len) { 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 */ @SuppressWarnings("unchecked") 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. */ public Object getArray() { return array; } /** * Gets the start index to loop from. * * @return the start index * @since 4.0 */ public int getStartIndex() { return this.startIndex; } /** * Gets the end index to loop to. * * @return the end index * @since 4.0 */ public int getEndIndex() { return this.endIndex; } /** * Resets the iterator back to the start index. */ public void reset() { this.index = this.startIndex; } }