J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package java.util; |
| 27 | |
| 28 | /** |
| 29 | * An iterator for lists that allows the programmer |
| 30 | * to traverse the list in either direction, modify |
| 31 | * the list during iteration, and obtain the iterator's |
| 32 | * current position in the list. A {@code ListIterator} |
| 33 | * has no current element; its <I>cursor position</I> always |
| 34 | * lies between the element that would be returned by a call |
| 35 | * to {@code previous()} and the element that would be |
| 36 | * returned by a call to {@code next()}. |
| 37 | * An iterator for a list of length {@code n} has {@code n+1} possible |
| 38 | * cursor positions, as illustrated by the carets ({@code ^}) below: |
| 39 | * <PRE> |
| 40 | * Element(0) Element(1) Element(2) ... Element(n-1) |
| 41 | * cursor positions: ^ ^ ^ ^ ^ |
| 42 | * </PRE> |
| 43 | * Note that the {@link #remove} and {@link #set(Object)} methods are |
| 44 | * <i>not</i> defined in terms of the cursor position; they are defined to |
| 45 | * operate on the last element returned by a call to {@link #next} or |
| 46 | * {@link #previous()}. |
| 47 | * |
| 48 | * <p>This interface is a member of the |
| 49 | * <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
| 50 | * Java Collections Framework</a>. |
| 51 | * |
| 52 | * @author Josh Bloch |
| 53 | * @see Collection |
| 54 | * @see List |
| 55 | * @see Iterator |
| 56 | * @see Enumeration |
| 57 | * @see List#listIterator() |
| 58 | * @since 1.2 |
| 59 | */ |
| 60 | public interface ListIterator<E> extends Iterator<E> { |
| 61 | // Query Operations |
| 62 | |
| 63 | /** |
| 64 | * Returns {@code true} if this list iterator has more elements when |
| 65 | * traversing the list in the forward direction. (In other words, |
| 66 | * returns {@code true} if {@link #next} would return an element rather |
| 67 | * than throwing an exception.) |
| 68 | * |
| 69 | * @return {@code true} if the list iterator has more elements when |
| 70 | * traversing the list in the forward direction |
| 71 | */ |
| 72 | boolean hasNext(); |
| 73 | |
| 74 | /** |
| 75 | * Returns the next element in the list and advances the cursor position. |
| 76 | * This method may be called repeatedly to iterate through the list, |
| 77 | * or intermixed with calls to {@link #previous} to go back and forth. |
| 78 | * (Note that alternating calls to {@code next} and {@code previous} |
| 79 | * will return the same element repeatedly.) |
| 80 | * |
| 81 | * @return the next element in the list |
| 82 | * @throws NoSuchElementException if the iteration has no next element |
| 83 | */ |
| 84 | E next(); |
| 85 | |
| 86 | /** |
| 87 | * Returns {@code true} if this list iterator has more elements when |
| 88 | * traversing the list in the reverse direction. (In other words, |
| 89 | * returns {@code true} if {@link #previous} would return an element |
| 90 | * rather than throwing an exception.) |
| 91 | * |
| 92 | * @return {@code true} if the list iterator has more elements when |
| 93 | * traversing the list in the reverse direction |
| 94 | */ |
| 95 | boolean hasPrevious(); |
| 96 | |
| 97 | /** |
| 98 | * Returns the previous element in the list and moves the cursor |
| 99 | * position backwards. This method may be called repeatedly to |
| 100 | * iterate through the list backwards, or intermixed with calls to |
| 101 | * {@link #next} to go back and forth. (Note that alternating calls |
| 102 | * to {@code next} and {@code previous} will return the same |
| 103 | * element repeatedly.) |
| 104 | * |
| 105 | * @return the previous element in the list |
| 106 | * @throws NoSuchElementException if the iteration has no previous |
| 107 | * element |
| 108 | */ |
| 109 | E previous(); |
| 110 | |
| 111 | /** |
| 112 | * Returns the index of the element that would be returned by a |
| 113 | * subsequent call to {@link #next}. (Returns list size if the list |
| 114 | * iterator is at the end of the list.) |
| 115 | * |
| 116 | * @return the index of the element that would be returned by a |
| 117 | * subsequent call to {@code next}, or list size if the list |
| 118 | * iterator is at the end of the list |
| 119 | */ |
| 120 | int nextIndex(); |
| 121 | |
| 122 | /** |
| 123 | * Returns the index of the element that would be returned by a |
| 124 | * subsequent call to {@link #previous}. (Returns -1 if the list |
| 125 | * iterator is at the beginning of the list.) |
| 126 | * |
| 127 | * @return the index of the element that would be returned by a |
| 128 | * subsequent call to {@code previous}, or -1 if the list |
| 129 | * iterator is at the beginning of the list |
| 130 | */ |
| 131 | int previousIndex(); |
| 132 | |
| 133 | |
| 134 | // Modification Operations |
| 135 | |
| 136 | /** |
| 137 | * Removes from the list the last element that was returned by {@link |
| 138 | * #next} or {@link #previous} (optional operation). This call can |
| 139 | * only be made once per call to {@code next} or {@code previous}. |
| 140 | * It can be made only if {@link #add} has not been |
| 141 | * called after the last call to {@code next} or {@code previous}. |
| 142 | * |
| 143 | * @throws UnsupportedOperationException if the {@code remove} |
| 144 | * operation is not supported by this list iterator |
| 145 | * @throws IllegalStateException if neither {@code next} nor |
| 146 | * {@code previous} have been called, or {@code remove} or |
| 147 | * {@code add} have been called after the last call to |
| 148 | * {@code next} or {@code previous} |
| 149 | */ |
| 150 | void remove(); |
| 151 | |
| 152 | /** |
| 153 | * Replaces the last element returned by {@link #next} or |
| 154 | * {@link #previous} with the specified element (optional operation). |
| 155 | * This call can be made only if neither {@link #remove} nor {@link |
| 156 | * #add} have been called after the last call to {@code next} or |
| 157 | * {@code previous}. |
| 158 | * |
| 159 | * @param e the element with which to replace the last element returned by |
| 160 | * {@code next} or {@code previous} |
| 161 | * @throws UnsupportedOperationException if the {@code set} operation |
| 162 | * is not supported by this list iterator |
| 163 | * @throws ClassCastException if the class of the specified element |
| 164 | * prevents it from being added to this list |
| 165 | * @throws IllegalArgumentException if some aspect of the specified |
| 166 | * element prevents it from being added to this list |
| 167 | * @throws IllegalStateException if neither {@code next} nor |
| 168 | * {@code previous} have been called, or {@code remove} or |
| 169 | * {@code add} have been called after the last call to |
| 170 | * {@code next} or {@code previous} |
| 171 | */ |
| 172 | void set(E e); |
| 173 | |
| 174 | /** |
| 175 | * Inserts the specified element into the list (optional operation). |
| 176 | * The element is inserted immediately before the next element that |
| 177 | * would be returned by {@link #next}, if any, and after the next |
| 178 | * element that would be returned by {@link #previous}, if any. (If the |
| 179 | * list contains no elements, the new element becomes the sole element |
| 180 | * on the list.) The new element is inserted before the implicit |
| 181 | * cursor: a subsequent call to {@code next} would be unaffected, and a |
| 182 | * subsequent call to {@code previous} would return the new element. |
| 183 | * (This call increases by one the value that would be returned by a |
| 184 | * call to {@code nextIndex} or {@code previousIndex}.) |
| 185 | * |
| 186 | * @param e the element to insert |
| 187 | * @throws UnsupportedOperationException if the {@code add} method is |
| 188 | * not supported by this list iterator |
| 189 | * @throws ClassCastException if the class of the specified element |
| 190 | * prevents it from being added to this list |
| 191 | * @throws IllegalArgumentException if some aspect of this element |
| 192 | * prevents it from being added to this list |
| 193 | */ |
| 194 | void add(E e); |
| 195 | } |