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| 1 | +/* | |
| 2 | + * Copyright (c) 1997, 2007, Oracle and/or its affiliates. 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. Oracle designates this | |
| 8 | + * particular file as subject to the "Classpath" exception as provided | |
| 9 | + * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 22 | + * or visit www.oracle.com if you need additional information or have any | |
| 23 | + * 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 element that | |
| 177 | + * would be returned by {@link #next}, if any, and after the element | |
| 178 | + * 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 | +} | |