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.util.NoSuchElementException; 020 021import org.apache.commons.collections4.ResettableListIterator; 022 023/** 024 * Implements a {@link java.util.ListIterator} over an array of objects. 025 * <p> 026 * This iterator does not support {@link #add} or {@link #remove}, as the object array 027 * cannot be structurally modified. The {@link #set} method is supported however. 028 * <p> 029 * The iterator implements a {@link #reset} method, allowing the reset of the iterator 030 * back to the start if required. 031 * 032 * @param <E> the type of elements returned by this iterator. 033 * @see org.apache.commons.collections4.iterators.ObjectArrayIterator 034 * @see java.util.Iterator 035 * @see java.util.ListIterator 036 * 037 * @since 3.0 038 */ 039public class ObjectArrayListIterator<E> extends ObjectArrayIterator<E> 040 implements ResettableListIterator<E> { 041 042 /** 043 * Holds the index of the last item returned by a call to {@code next()} 044 * or {@code previous()}. This is set to {@code -1} if neither method 045 * has yet been invoked. {@code lastItemIndex} is used to implement the 046 * {@link #set} method. 047 */ 048 private int lastItemIndex = -1; 049 050 /** 051 * Constructs an ObjectArrayListIterator that will iterate over the values in the 052 * specified array. 053 * 054 * @param array the array to iterate over 055 * @throws NullPointerException if {@code array} is {@code null} 056 */ 057 public ObjectArrayListIterator(final E... array) { 058 super(array); 059 } 060 061 /** 062 * Constructs an ObjectArrayListIterator that will iterate over the values in the 063 * specified array from a specific start index. 064 * 065 * @param array the array to iterate over 066 * @param start the index to start iterating at 067 * @throws NullPointerException if {@code array} is {@code null} 068 * @throws IndexOutOfBoundsException if the start index is out of bounds 069 */ 070 public ObjectArrayListIterator(final E[] array, final int start) { 071 super(array, start); 072 } 073 074 /** 075 * Constructs an ObjectArrayListIterator that will iterate over a range of values 076 * in the specified array. 077 * 078 * @param array the array to iterate over 079 * @param start the index to start iterating at 080 * @param end the index (exclusive) to finish iterating at 081 * @throws IndexOutOfBoundsException if the start or end index is out of bounds 082 * @throws IllegalArgumentException if end index is before the start 083 * @throws NullPointerException if {@code array} is {@code null} 084 */ 085 public ObjectArrayListIterator(final E[] array, final int start, final int end) { 086 super(array, start, end); 087 } 088 089 /** 090 * This iterator does not support modification of its backing array's size, and so will 091 * always throw an {@link UnsupportedOperationException} when this method is invoked. 092 * 093 * @param obj the object to add 094 * @throws UnsupportedOperationException always thrown. 095 */ 096 @Override 097 public void add(final E obj) { 098 throw new UnsupportedOperationException("add() method is not supported"); 099 } 100 101 /** 102 * Returns true if there are previous elements to return from the array. 103 * 104 * @return true if there is a previous element to return 105 */ 106 @Override 107 public boolean hasPrevious() { 108 return this.index > getStartIndex(); 109 } 110 111 /** 112 * Gets the next element from the array. 113 * 114 * @return the next element 115 * @throws NoSuchElementException if there is no next element 116 */ 117 @Override 118 public E next() { 119 if (!hasNext()) { 120 throw new NoSuchElementException(); 121 } 122 this.lastItemIndex = this.index; 123 return this.array[this.index++]; 124 } 125 126 /** 127 * Gets the next index to be retrieved. 128 * 129 * @return the index of the item to be retrieved next 130 */ 131 @Override 132 public int nextIndex() { 133 return this.index - getStartIndex(); 134 } 135 136 /** 137 * Gets the previous element from the array. 138 * 139 * @return the previous element 140 * @throws NoSuchElementException if there is no previous element 141 */ 142 @Override 143 public E previous() { 144 if (!hasPrevious()) { 145 throw new NoSuchElementException(); 146 } 147 this.lastItemIndex = --this.index; 148 return this.array[this.index]; 149 } 150 151 /** 152 * Gets the index of the item to be retrieved if {@link #previous()} is called. 153 * 154 * @return the index of the item to be retrieved next 155 */ 156 @Override 157 public int previousIndex() { 158 return this.index - getStartIndex() - 1; 159 } 160 161 /** 162 * Resets the iterator back to the start index. 163 */ 164 @Override 165 public void reset() { 166 super.reset(); 167 this.lastItemIndex = -1; 168 } 169 170 /** 171 * Sets the element under the cursor. 172 * <p> 173 * This method sets the element that was returned by the last call 174 * to {@link #next()} of {@link #previous()}. 175 * 176 * <b>Note:</b> {@link java.util.ListIterator} implementations that support {@code add()} 177 * and {@code remove()} only allow {@code set()} to be called once per call 178 * to {@code next()} or {@code previous} (see the {@link java.util.ListIterator} 179 * Javadoc for more details). Since this implementation does not support 180 * {@code add()} or {@code remove()}, {@code set()} may be 181 * called as often as desired. 182 * 183 * @param obj the object to set into the array 184 * @throws IllegalStateException if next() has not yet been called. 185 * @throws ClassCastException if the object type is unsuitable for the array 186 */ 187 @Override 188 public void set(final E obj) { 189 if (this.lastItemIndex == -1) { 190 throw new IllegalStateException("must call next() or previous() before a call to set()"); 191 } 192 193 this.array[this.lastItemIndex] = obj; 194 } 195 196}