1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/rt/emul/compact/src/main/java/java/util/LinkedList.java Tue Feb 26 16:54:16 2013 +0100
1.3 @@ -0,0 +1,1100 @@
1.4 +/*
1.5 + * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation. Oracle designates this
1.11 + * particular file as subject to the "Classpath" exception as provided
1.12 + * by Oracle in the LICENSE file that accompanied this code.
1.13 + *
1.14 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.15 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.16 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.17 + * version 2 for more details (a copy is included in the LICENSE file that
1.18 + * accompanied this code).
1.19 + *
1.20 + * You should have received a copy of the GNU General Public License version
1.21 + * 2 along with this work; if not, write to the Free Software Foundation,
1.22 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.23 + *
1.24 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.25 + * or visit www.oracle.com if you need additional information or have any
1.26 + * questions.
1.27 + */
1.28 +
1.29 +package java.util;
1.30 +
1.31 +/**
1.32 + * Doubly-linked list implementation of the {@code List} and {@code Deque}
1.33 + * interfaces. Implements all optional list operations, and permits all
1.34 + * elements (including {@code null}).
1.35 + *
1.36 + * <p>All of the operations perform as could be expected for a doubly-linked
1.37 + * list. Operations that index into the list will traverse the list from
1.38 + * the beginning or the end, whichever is closer to the specified index.
1.39 + *
1.40 + * <p><strong>Note that this implementation is not synchronized.</strong>
1.41 + * If multiple threads access a linked list concurrently, and at least
1.42 + * one of the threads modifies the list structurally, it <i>must</i> be
1.43 + * synchronized externally. (A structural modification is any operation
1.44 + * that adds or deletes one or more elements; merely setting the value of
1.45 + * an element is not a structural modification.) This is typically
1.46 + * accomplished by synchronizing on some object that naturally
1.47 + * encapsulates the list.
1.48 + *
1.49 + * If no such object exists, the list should be "wrapped" using the
1.50 + * {@link Collections#synchronizedList Collections.synchronizedList}
1.51 + * method. This is best done at creation time, to prevent accidental
1.52 + * unsynchronized access to the list:<pre>
1.53 + * List list = Collections.synchronizedList(new LinkedList(...));</pre>
1.54 + *
1.55 + * <p>The iterators returned by this class's {@code iterator} and
1.56 + * {@code listIterator} methods are <i>fail-fast</i>: if the list is
1.57 + * structurally modified at any time after the iterator is created, in
1.58 + * any way except through the Iterator's own {@code remove} or
1.59 + * {@code add} methods, the iterator will throw a {@link
1.60 + * ConcurrentModificationException}. Thus, in the face of concurrent
1.61 + * modification, the iterator fails quickly and cleanly, rather than
1.62 + * risking arbitrary, non-deterministic behavior at an undetermined
1.63 + * time in the future.
1.64 + *
1.65 + * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
1.66 + * as it is, generally speaking, impossible to make any hard guarantees in the
1.67 + * presence of unsynchronized concurrent modification. Fail-fast iterators
1.68 + * throw {@code ConcurrentModificationException} on a best-effort basis.
1.69 + * Therefore, it would be wrong to write a program that depended on this
1.70 + * exception for its correctness: <i>the fail-fast behavior of iterators
1.71 + * should be used only to detect bugs.</i>
1.72 + *
1.73 + * <p>This class is a member of the
1.74 + * <a href="{@docRoot}/../technotes/guides/collections/index.html">
1.75 + * Java Collections Framework</a>.
1.76 + *
1.77 + * @author Josh Bloch
1.78 + * @see List
1.79 + * @see ArrayList
1.80 + * @since 1.2
1.81 + * @param <E> the type of elements held in this collection
1.82 + */
1.83 +
1.84 +public class LinkedList<E>
1.85 + extends AbstractSequentialList<E>
1.86 + implements List<E>, Deque<E>, Cloneable, java.io.Serializable
1.87 +{
1.88 + transient int size = 0;
1.89 +
1.90 + /**
1.91 + * Pointer to first node.
1.92 + * Invariant: (first == null && last == null) ||
1.93 + * (first.prev == null && first.item != null)
1.94 + */
1.95 + transient Node<E> first;
1.96 +
1.97 + /**
1.98 + * Pointer to last node.
1.99 + * Invariant: (first == null && last == null) ||
1.100 + * (last.next == null && last.item != null)
1.101 + */
1.102 + transient Node<E> last;
1.103 +
1.104 + /**
1.105 + * Constructs an empty list.
1.106 + */
1.107 + public LinkedList() {
1.108 + }
1.109 +
1.110 + /**
1.111 + * Constructs a list containing the elements of the specified
1.112 + * collection, in the order they are returned by the collection's
1.113 + * iterator.
1.114 + *
1.115 + * @param c the collection whose elements are to be placed into this list
1.116 + * @throws NullPointerException if the specified collection is null
1.117 + */
1.118 + public LinkedList(Collection<? extends E> c) {
1.119 + this();
1.120 + addAll(c);
1.121 + }
1.122 +
1.123 + /**
1.124 + * Links e as first element.
1.125 + */
1.126 + private void linkFirst(E e) {
1.127 + final Node<E> f = first;
1.128 + final Node<E> newNode = new Node<>(null, e, f);
1.129 + first = newNode;
1.130 + if (f == null)
1.131 + last = newNode;
1.132 + else
1.133 + f.prev = newNode;
1.134 + size++;
1.135 + modCount++;
1.136 + }
1.137 +
1.138 + /**
1.139 + * Links e as last element.
1.140 + */
1.141 + void linkLast(E e) {
1.142 + final Node<E> l = last;
1.143 + final Node<E> newNode = new Node<>(l, e, null);
1.144 + last = newNode;
1.145 + if (l == null)
1.146 + first = newNode;
1.147 + else
1.148 + l.next = newNode;
1.149 + size++;
1.150 + modCount++;
1.151 + }
1.152 +
1.153 + /**
1.154 + * Inserts element e before non-null Node succ.
1.155 + */
1.156 + void linkBefore(E e, Node<E> succ) {
1.157 + // assert succ != null;
1.158 + final Node<E> pred = succ.prev;
1.159 + final Node<E> newNode = new Node<>(pred, e, succ);
1.160 + succ.prev = newNode;
1.161 + if (pred == null)
1.162 + first = newNode;
1.163 + else
1.164 + pred.next = newNode;
1.165 + size++;
1.166 + modCount++;
1.167 + }
1.168 +
1.169 + /**
1.170 + * Unlinks non-null first node f.
1.171 + */
1.172 + private E unlinkFirst(Node<E> f) {
1.173 + // assert f == first && f != null;
1.174 + final E element = f.item;
1.175 + final Node<E> next = f.next;
1.176 + f.item = null;
1.177 + f.next = null; // help GC
1.178 + first = next;
1.179 + if (next == null)
1.180 + last = null;
1.181 + else
1.182 + next.prev = null;
1.183 + size--;
1.184 + modCount++;
1.185 + return element;
1.186 + }
1.187 +
1.188 + /**
1.189 + * Unlinks non-null last node l.
1.190 + */
1.191 + private E unlinkLast(Node<E> l) {
1.192 + // assert l == last && l != null;
1.193 + final E element = l.item;
1.194 + final Node<E> prev = l.prev;
1.195 + l.item = null;
1.196 + l.prev = null; // help GC
1.197 + last = prev;
1.198 + if (prev == null)
1.199 + first = null;
1.200 + else
1.201 + prev.next = null;
1.202 + size--;
1.203 + modCount++;
1.204 + return element;
1.205 + }
1.206 +
1.207 + /**
1.208 + * Unlinks non-null node x.
1.209 + */
1.210 + E unlink(Node<E> x) {
1.211 + // assert x != null;
1.212 + final E element = x.item;
1.213 + final Node<E> next = x.next;
1.214 + final Node<E> prev = x.prev;
1.215 +
1.216 + if (prev == null) {
1.217 + first = next;
1.218 + } else {
1.219 + prev.next = next;
1.220 + x.prev = null;
1.221 + }
1.222 +
1.223 + if (next == null) {
1.224 + last = prev;
1.225 + } else {
1.226 + next.prev = prev;
1.227 + x.next = null;
1.228 + }
1.229 +
1.230 + x.item = null;
1.231 + size--;
1.232 + modCount++;
1.233 + return element;
1.234 + }
1.235 +
1.236 + /**
1.237 + * Returns the first element in this list.
1.238 + *
1.239 + * @return the first element in this list
1.240 + * @throws NoSuchElementException if this list is empty
1.241 + */
1.242 + public E getFirst() {
1.243 + final Node<E> f = first;
1.244 + if (f == null)
1.245 + throw new NoSuchElementException();
1.246 + return f.item;
1.247 + }
1.248 +
1.249 + /**
1.250 + * Returns the last element in this list.
1.251 + *
1.252 + * @return the last element in this list
1.253 + * @throws NoSuchElementException if this list is empty
1.254 + */
1.255 + public E getLast() {
1.256 + final Node<E> l = last;
1.257 + if (l == null)
1.258 + throw new NoSuchElementException();
1.259 + return l.item;
1.260 + }
1.261 +
1.262 + /**
1.263 + * Removes and returns the first element from this list.
1.264 + *
1.265 + * @return the first element from this list
1.266 + * @throws NoSuchElementException if this list is empty
1.267 + */
1.268 + public E removeFirst() {
1.269 + final Node<E> f = first;
1.270 + if (f == null)
1.271 + throw new NoSuchElementException();
1.272 + return unlinkFirst(f);
1.273 + }
1.274 +
1.275 + /**
1.276 + * Removes and returns the last element from this list.
1.277 + *
1.278 + * @return the last element from this list
1.279 + * @throws NoSuchElementException if this list is empty
1.280 + */
1.281 + public E removeLast() {
1.282 + final Node<E> l = last;
1.283 + if (l == null)
1.284 + throw new NoSuchElementException();
1.285 + return unlinkLast(l);
1.286 + }
1.287 +
1.288 + /**
1.289 + * Inserts the specified element at the beginning of this list.
1.290 + *
1.291 + * @param e the element to add
1.292 + */
1.293 + public void addFirst(E e) {
1.294 + linkFirst(e);
1.295 + }
1.296 +
1.297 + /**
1.298 + * Appends the specified element to the end of this list.
1.299 + *
1.300 + * <p>This method is equivalent to {@link #add}.
1.301 + *
1.302 + * @param e the element to add
1.303 + */
1.304 + public void addLast(E e) {
1.305 + linkLast(e);
1.306 + }
1.307 +
1.308 + /**
1.309 + * Returns {@code true} if this list contains the specified element.
1.310 + * More formally, returns {@code true} if and only if this list contains
1.311 + * at least one element {@code e} such that
1.312 + * <tt>(o==null ? e==null : o.equals(e))</tt>.
1.313 + *
1.314 + * @param o element whose presence in this list is to be tested
1.315 + * @return {@code true} if this list contains the specified element
1.316 + */
1.317 + public boolean contains(Object o) {
1.318 + return indexOf(o) != -1;
1.319 + }
1.320 +
1.321 + /**
1.322 + * Returns the number of elements in this list.
1.323 + *
1.324 + * @return the number of elements in this list
1.325 + */
1.326 + public int size() {
1.327 + return size;
1.328 + }
1.329 +
1.330 + /**
1.331 + * Appends the specified element to the end of this list.
1.332 + *
1.333 + * <p>This method is equivalent to {@link #addLast}.
1.334 + *
1.335 + * @param e element to be appended to this list
1.336 + * @return {@code true} (as specified by {@link Collection#add})
1.337 + */
1.338 + public boolean add(E e) {
1.339 + linkLast(e);
1.340 + return true;
1.341 + }
1.342 +
1.343 + /**
1.344 + * Removes the first occurrence of the specified element from this list,
1.345 + * if it is present. If this list does not contain the element, it is
1.346 + * unchanged. More formally, removes the element with the lowest index
1.347 + * {@code i} such that
1.348 + * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>
1.349 + * (if such an element exists). Returns {@code true} if this list
1.350 + * contained the specified element (or equivalently, if this list
1.351 + * changed as a result of the call).
1.352 + *
1.353 + * @param o element to be removed from this list, if present
1.354 + * @return {@code true} if this list contained the specified element
1.355 + */
1.356 + public boolean remove(Object o) {
1.357 + if (o == null) {
1.358 + for (Node<E> x = first; x != null; x = x.next) {
1.359 + if (x.item == null) {
1.360 + unlink(x);
1.361 + return true;
1.362 + }
1.363 + }
1.364 + } else {
1.365 + for (Node<E> x = first; x != null; x = x.next) {
1.366 + if (o.equals(x.item)) {
1.367 + unlink(x);
1.368 + return true;
1.369 + }
1.370 + }
1.371 + }
1.372 + return false;
1.373 + }
1.374 +
1.375 + /**
1.376 + * Appends all of the elements in the specified collection to the end of
1.377 + * this list, in the order that they are returned by the specified
1.378 + * collection's iterator. The behavior of this operation is undefined if
1.379 + * the specified collection is modified while the operation is in
1.380 + * progress. (Note that this will occur if the specified collection is
1.381 + * this list, and it's nonempty.)
1.382 + *
1.383 + * @param c collection containing elements to be added to this list
1.384 + * @return {@code true} if this list changed as a result of the call
1.385 + * @throws NullPointerException if the specified collection is null
1.386 + */
1.387 + public boolean addAll(Collection<? extends E> c) {
1.388 + return addAll(size, c);
1.389 + }
1.390 +
1.391 + /**
1.392 + * Inserts all of the elements in the specified collection into this
1.393 + * list, starting at the specified position. Shifts the element
1.394 + * currently at that position (if any) and any subsequent elements to
1.395 + * the right (increases their indices). The new elements will appear
1.396 + * in the list in the order that they are returned by the
1.397 + * specified collection's iterator.
1.398 + *
1.399 + * @param index index at which to insert the first element
1.400 + * from the specified collection
1.401 + * @param c collection containing elements to be added to this list
1.402 + * @return {@code true} if this list changed as a result of the call
1.403 + * @throws IndexOutOfBoundsException {@inheritDoc}
1.404 + * @throws NullPointerException if the specified collection is null
1.405 + */
1.406 + public boolean addAll(int index, Collection<? extends E> c) {
1.407 + checkPositionIndex(index);
1.408 +
1.409 + Object[] a = c.toArray();
1.410 + int numNew = a.length;
1.411 + if (numNew == 0)
1.412 + return false;
1.413 +
1.414 + Node<E> pred, succ;
1.415 + if (index == size) {
1.416 + succ = null;
1.417 + pred = last;
1.418 + } else {
1.419 + succ = node(index);
1.420 + pred = succ.prev;
1.421 + }
1.422 +
1.423 + for (Object o : a) {
1.424 + @SuppressWarnings("unchecked") E e = (E) o;
1.425 + Node<E> newNode = new Node<>(pred, e, null);
1.426 + if (pred == null)
1.427 + first = newNode;
1.428 + else
1.429 + pred.next = newNode;
1.430 + pred = newNode;
1.431 + }
1.432 +
1.433 + if (succ == null) {
1.434 + last = pred;
1.435 + } else {
1.436 + pred.next = succ;
1.437 + succ.prev = pred;
1.438 + }
1.439 +
1.440 + size += numNew;
1.441 + modCount++;
1.442 + return true;
1.443 + }
1.444 +
1.445 + /**
1.446 + * Removes all of the elements from this list.
1.447 + * The list will be empty after this call returns.
1.448 + */
1.449 + public void clear() {
1.450 + // Clearing all of the links between nodes is "unnecessary", but:
1.451 + // - helps a generational GC if the discarded nodes inhabit
1.452 + // more than one generation
1.453 + // - is sure to free memory even if there is a reachable Iterator
1.454 + for (Node<E> x = first; x != null; ) {
1.455 + Node<E> next = x.next;
1.456 + x.item = null;
1.457 + x.next = null;
1.458 + x.prev = null;
1.459 + x = next;
1.460 + }
1.461 + first = last = null;
1.462 + size = 0;
1.463 + modCount++;
1.464 + }
1.465 +
1.466 +
1.467 + // Positional Access Operations
1.468 +
1.469 + /**
1.470 + * Returns the element at the specified position in this list.
1.471 + *
1.472 + * @param index index of the element to return
1.473 + * @return the element at the specified position in this list
1.474 + * @throws IndexOutOfBoundsException {@inheritDoc}
1.475 + */
1.476 + public E get(int index) {
1.477 + checkElementIndex(index);
1.478 + return node(index).item;
1.479 + }
1.480 +
1.481 + /**
1.482 + * Replaces the element at the specified position in this list with the
1.483 + * specified element.
1.484 + *
1.485 + * @param index index of the element to replace
1.486 + * @param element element to be stored at the specified position
1.487 + * @return the element previously at the specified position
1.488 + * @throws IndexOutOfBoundsException {@inheritDoc}
1.489 + */
1.490 + public E set(int index, E element) {
1.491 + checkElementIndex(index);
1.492 + Node<E> x = node(index);
1.493 + E oldVal = x.item;
1.494 + x.item = element;
1.495 + return oldVal;
1.496 + }
1.497 +
1.498 + /**
1.499 + * Inserts the specified element at the specified position in this list.
1.500 + * Shifts the element currently at that position (if any) and any
1.501 + * subsequent elements to the right (adds one to their indices).
1.502 + *
1.503 + * @param index index at which the specified element is to be inserted
1.504 + * @param element element to be inserted
1.505 + * @throws IndexOutOfBoundsException {@inheritDoc}
1.506 + */
1.507 + public void add(int index, E element) {
1.508 + checkPositionIndex(index);
1.509 +
1.510 + if (index == size)
1.511 + linkLast(element);
1.512 + else
1.513 + linkBefore(element, node(index));
1.514 + }
1.515 +
1.516 + /**
1.517 + * Removes the element at the specified position in this list. Shifts any
1.518 + * subsequent elements to the left (subtracts one from their indices).
1.519 + * Returns the element that was removed from the list.
1.520 + *
1.521 + * @param index the index of the element to be removed
1.522 + * @return the element previously at the specified position
1.523 + * @throws IndexOutOfBoundsException {@inheritDoc}
1.524 + */
1.525 + public E remove(int index) {
1.526 + checkElementIndex(index);
1.527 + return unlink(node(index));
1.528 + }
1.529 +
1.530 + /**
1.531 + * Tells if the argument is the index of an existing element.
1.532 + */
1.533 + private boolean isElementIndex(int index) {
1.534 + return index >= 0 && index < size;
1.535 + }
1.536 +
1.537 + /**
1.538 + * Tells if the argument is the index of a valid position for an
1.539 + * iterator or an add operation.
1.540 + */
1.541 + private boolean isPositionIndex(int index) {
1.542 + return index >= 0 && index <= size;
1.543 + }
1.544 +
1.545 + /**
1.546 + * Constructs an IndexOutOfBoundsException detail message.
1.547 + * Of the many possible refactorings of the error handling code,
1.548 + * this "outlining" performs best with both server and client VMs.
1.549 + */
1.550 + private String outOfBoundsMsg(int index) {
1.551 + return "Index: "+index+", Size: "+size;
1.552 + }
1.553 +
1.554 + private void checkElementIndex(int index) {
1.555 + if (!isElementIndex(index))
1.556 + throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1.557 + }
1.558 +
1.559 + private void checkPositionIndex(int index) {
1.560 + if (!isPositionIndex(index))
1.561 + throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1.562 + }
1.563 +
1.564 + /**
1.565 + * Returns the (non-null) Node at the specified element index.
1.566 + */
1.567 + Node<E> node(int index) {
1.568 + // assert isElementIndex(index);
1.569 +
1.570 + if (index < (size >> 1)) {
1.571 + Node<E> x = first;
1.572 + for (int i = 0; i < index; i++)
1.573 + x = x.next;
1.574 + return x;
1.575 + } else {
1.576 + Node<E> x = last;
1.577 + for (int i = size - 1; i > index; i--)
1.578 + x = x.prev;
1.579 + return x;
1.580 + }
1.581 + }
1.582 +
1.583 + // Search Operations
1.584 +
1.585 + /**
1.586 + * Returns the index of the first occurrence of the specified element
1.587 + * in this list, or -1 if this list does not contain the element.
1.588 + * More formally, returns the lowest index {@code i} such that
1.589 + * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
1.590 + * or -1 if there is no such index.
1.591 + *
1.592 + * @param o element to search for
1.593 + * @return the index of the first occurrence of the specified element in
1.594 + * this list, or -1 if this list does not contain the element
1.595 + */
1.596 + public int indexOf(Object o) {
1.597 + int index = 0;
1.598 + if (o == null) {
1.599 + for (Node<E> x = first; x != null; x = x.next) {
1.600 + if (x.item == null)
1.601 + return index;
1.602 + index++;
1.603 + }
1.604 + } else {
1.605 + for (Node<E> x = first; x != null; x = x.next) {
1.606 + if (o.equals(x.item))
1.607 + return index;
1.608 + index++;
1.609 + }
1.610 + }
1.611 + return -1;
1.612 + }
1.613 +
1.614 + /**
1.615 + * Returns the index of the last occurrence of the specified element
1.616 + * in this list, or -1 if this list does not contain the element.
1.617 + * More formally, returns the highest index {@code i} such that
1.618 + * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
1.619 + * or -1 if there is no such index.
1.620 + *
1.621 + * @param o element to search for
1.622 + * @return the index of the last occurrence of the specified element in
1.623 + * this list, or -1 if this list does not contain the element
1.624 + */
1.625 + public int lastIndexOf(Object o) {
1.626 + int index = size;
1.627 + if (o == null) {
1.628 + for (Node<E> x = last; x != null; x = x.prev) {
1.629 + index--;
1.630 + if (x.item == null)
1.631 + return index;
1.632 + }
1.633 + } else {
1.634 + for (Node<E> x = last; x != null; x = x.prev) {
1.635 + index--;
1.636 + if (o.equals(x.item))
1.637 + return index;
1.638 + }
1.639 + }
1.640 + return -1;
1.641 + }
1.642 +
1.643 + // Queue operations.
1.644 +
1.645 + /**
1.646 + * Retrieves, but does not remove, the head (first element) of this list.
1.647 + *
1.648 + * @return the head of this list, or {@code null} if this list is empty
1.649 + * @since 1.5
1.650 + */
1.651 + public E peek() {
1.652 + final Node<E> f = first;
1.653 + return (f == null) ? null : f.item;
1.654 + }
1.655 +
1.656 + /**
1.657 + * Retrieves, but does not remove, the head (first element) of this list.
1.658 + *
1.659 + * @return the head of this list
1.660 + * @throws NoSuchElementException if this list is empty
1.661 + * @since 1.5
1.662 + */
1.663 + public E element() {
1.664 + return getFirst();
1.665 + }
1.666 +
1.667 + /**
1.668 + * Retrieves and removes the head (first element) of this list.
1.669 + *
1.670 + * @return the head of this list, or {@code null} if this list is empty
1.671 + * @since 1.5
1.672 + */
1.673 + public E poll() {
1.674 + final Node<E> f = first;
1.675 + return (f == null) ? null : unlinkFirst(f);
1.676 + }
1.677 +
1.678 + /**
1.679 + * Retrieves and removes the head (first element) of this list.
1.680 + *
1.681 + * @return the head of this list
1.682 + * @throws NoSuchElementException if this list is empty
1.683 + * @since 1.5
1.684 + */
1.685 + public E remove() {
1.686 + return removeFirst();
1.687 + }
1.688 +
1.689 + /**
1.690 + * Adds the specified element as the tail (last element) of this list.
1.691 + *
1.692 + * @param e the element to add
1.693 + * @return {@code true} (as specified by {@link Queue#offer})
1.694 + * @since 1.5
1.695 + */
1.696 + public boolean offer(E e) {
1.697 + return add(e);
1.698 + }
1.699 +
1.700 + // Deque operations
1.701 + /**
1.702 + * Inserts the specified element at the front of this list.
1.703 + *
1.704 + * @param e the element to insert
1.705 + * @return {@code true} (as specified by {@link Deque#offerFirst})
1.706 + * @since 1.6
1.707 + */
1.708 + public boolean offerFirst(E e) {
1.709 + addFirst(e);
1.710 + return true;
1.711 + }
1.712 +
1.713 + /**
1.714 + * Inserts the specified element at the end of this list.
1.715 + *
1.716 + * @param e the element to insert
1.717 + * @return {@code true} (as specified by {@link Deque#offerLast})
1.718 + * @since 1.6
1.719 + */
1.720 + public boolean offerLast(E e) {
1.721 + addLast(e);
1.722 + return true;
1.723 + }
1.724 +
1.725 + /**
1.726 + * Retrieves, but does not remove, the first element of this list,
1.727 + * or returns {@code null} if this list is empty.
1.728 + *
1.729 + * @return the first element of this list, or {@code null}
1.730 + * if this list is empty
1.731 + * @since 1.6
1.732 + */
1.733 + public E peekFirst() {
1.734 + final Node<E> f = first;
1.735 + return (f == null) ? null : f.item;
1.736 + }
1.737 +
1.738 + /**
1.739 + * Retrieves, but does not remove, the last element of this list,
1.740 + * or returns {@code null} if this list is empty.
1.741 + *
1.742 + * @return the last element of this list, or {@code null}
1.743 + * if this list is empty
1.744 + * @since 1.6
1.745 + */
1.746 + public E peekLast() {
1.747 + final Node<E> l = last;
1.748 + return (l == null) ? null : l.item;
1.749 + }
1.750 +
1.751 + /**
1.752 + * Retrieves and removes the first element of this list,
1.753 + * or returns {@code null} if this list is empty.
1.754 + *
1.755 + * @return the first element of this list, or {@code null} if
1.756 + * this list is empty
1.757 + * @since 1.6
1.758 + */
1.759 + public E pollFirst() {
1.760 + final Node<E> f = first;
1.761 + return (f == null) ? null : unlinkFirst(f);
1.762 + }
1.763 +
1.764 + /**
1.765 + * Retrieves and removes the last element of this list,
1.766 + * or returns {@code null} if this list is empty.
1.767 + *
1.768 + * @return the last element of this list, or {@code null} if
1.769 + * this list is empty
1.770 + * @since 1.6
1.771 + */
1.772 + public E pollLast() {
1.773 + final Node<E> l = last;
1.774 + return (l == null) ? null : unlinkLast(l);
1.775 + }
1.776 +
1.777 + /**
1.778 + * Pushes an element onto the stack represented by this list. In other
1.779 + * words, inserts the element at the front of this list.
1.780 + *
1.781 + * <p>This method is equivalent to {@link #addFirst}.
1.782 + *
1.783 + * @param e the element to push
1.784 + * @since 1.6
1.785 + */
1.786 + public void push(E e) {
1.787 + addFirst(e);
1.788 + }
1.789 +
1.790 + /**
1.791 + * Pops an element from the stack represented by this list. In other
1.792 + * words, removes and returns the first element of this list.
1.793 + *
1.794 + * <p>This method is equivalent to {@link #removeFirst()}.
1.795 + *
1.796 + * @return the element at the front of this list (which is the top
1.797 + * of the stack represented by this list)
1.798 + * @throws NoSuchElementException if this list is empty
1.799 + * @since 1.6
1.800 + */
1.801 + public E pop() {
1.802 + return removeFirst();
1.803 + }
1.804 +
1.805 + /**
1.806 + * Removes the first occurrence of the specified element in this
1.807 + * list (when traversing the list from head to tail). If the list
1.808 + * does not contain the element, it is unchanged.
1.809 + *
1.810 + * @param o element to be removed from this list, if present
1.811 + * @return {@code true} if the list contained the specified element
1.812 + * @since 1.6
1.813 + */
1.814 + public boolean removeFirstOccurrence(Object o) {
1.815 + return remove(o);
1.816 + }
1.817 +
1.818 + /**
1.819 + * Removes the last occurrence of the specified element in this
1.820 + * list (when traversing the list from head to tail). If the list
1.821 + * does not contain the element, it is unchanged.
1.822 + *
1.823 + * @param o element to be removed from this list, if present
1.824 + * @return {@code true} if the list contained the specified element
1.825 + * @since 1.6
1.826 + */
1.827 + public boolean removeLastOccurrence(Object o) {
1.828 + if (o == null) {
1.829 + for (Node<E> x = last; x != null; x = x.prev) {
1.830 + if (x.item == null) {
1.831 + unlink(x);
1.832 + return true;
1.833 + }
1.834 + }
1.835 + } else {
1.836 + for (Node<E> x = last; x != null; x = x.prev) {
1.837 + if (o.equals(x.item)) {
1.838 + unlink(x);
1.839 + return true;
1.840 + }
1.841 + }
1.842 + }
1.843 + return false;
1.844 + }
1.845 +
1.846 + /**
1.847 + * Returns a list-iterator of the elements in this list (in proper
1.848 + * sequence), starting at the specified position in the list.
1.849 + * Obeys the general contract of {@code List.listIterator(int)}.<p>
1.850 + *
1.851 + * The list-iterator is <i>fail-fast</i>: if the list is structurally
1.852 + * modified at any time after the Iterator is created, in any way except
1.853 + * through the list-iterator's own {@code remove} or {@code add}
1.854 + * methods, the list-iterator will throw a
1.855 + * {@code ConcurrentModificationException}. Thus, in the face of
1.856 + * concurrent modification, the iterator fails quickly and cleanly, rather
1.857 + * than risking arbitrary, non-deterministic behavior at an undetermined
1.858 + * time in the future.
1.859 + *
1.860 + * @param index index of the first element to be returned from the
1.861 + * list-iterator (by a call to {@code next})
1.862 + * @return a ListIterator of the elements in this list (in proper
1.863 + * sequence), starting at the specified position in the list
1.864 + * @throws IndexOutOfBoundsException {@inheritDoc}
1.865 + * @see List#listIterator(int)
1.866 + */
1.867 + public ListIterator<E> listIterator(int index) {
1.868 + checkPositionIndex(index);
1.869 + return new ListItr(index);
1.870 + }
1.871 +
1.872 + private class ListItr implements ListIterator<E> {
1.873 + private Node<E> lastReturned = null;
1.874 + private Node<E> next;
1.875 + private int nextIndex;
1.876 + private int expectedModCount = modCount;
1.877 +
1.878 + ListItr(int index) {
1.879 + // assert isPositionIndex(index);
1.880 + next = (index == size) ? null : node(index);
1.881 + nextIndex = index;
1.882 + }
1.883 +
1.884 + public boolean hasNext() {
1.885 + return nextIndex < size;
1.886 + }
1.887 +
1.888 + public E next() {
1.889 + checkForComodification();
1.890 + if (!hasNext())
1.891 + throw new NoSuchElementException();
1.892 +
1.893 + lastReturned = next;
1.894 + next = next.next;
1.895 + nextIndex++;
1.896 + return lastReturned.item;
1.897 + }
1.898 +
1.899 + public boolean hasPrevious() {
1.900 + return nextIndex > 0;
1.901 + }
1.902 +
1.903 + public E previous() {
1.904 + checkForComodification();
1.905 + if (!hasPrevious())
1.906 + throw new NoSuchElementException();
1.907 +
1.908 + lastReturned = next = (next == null) ? last : next.prev;
1.909 + nextIndex--;
1.910 + return lastReturned.item;
1.911 + }
1.912 +
1.913 + public int nextIndex() {
1.914 + return nextIndex;
1.915 + }
1.916 +
1.917 + public int previousIndex() {
1.918 + return nextIndex - 1;
1.919 + }
1.920 +
1.921 + public void remove() {
1.922 + checkForComodification();
1.923 + if (lastReturned == null)
1.924 + throw new IllegalStateException();
1.925 +
1.926 + Node<E> lastNext = lastReturned.next;
1.927 + unlink(lastReturned);
1.928 + if (next == lastReturned)
1.929 + next = lastNext;
1.930 + else
1.931 + nextIndex--;
1.932 + lastReturned = null;
1.933 + expectedModCount++;
1.934 + }
1.935 +
1.936 + public void set(E e) {
1.937 + if (lastReturned == null)
1.938 + throw new IllegalStateException();
1.939 + checkForComodification();
1.940 + lastReturned.item = e;
1.941 + }
1.942 +
1.943 + public void add(E e) {
1.944 + checkForComodification();
1.945 + lastReturned = null;
1.946 + if (next == null)
1.947 + linkLast(e);
1.948 + else
1.949 + linkBefore(e, next);
1.950 + nextIndex++;
1.951 + expectedModCount++;
1.952 + }
1.953 +
1.954 + final void checkForComodification() {
1.955 + if (modCount != expectedModCount)
1.956 + throw new ConcurrentModificationException();
1.957 + }
1.958 + }
1.959 +
1.960 + private static class Node<E> {
1.961 + E item;
1.962 + Node<E> next;
1.963 + Node<E> prev;
1.964 +
1.965 + Node(Node<E> prev, E element, Node<E> next) {
1.966 + this.item = element;
1.967 + this.next = next;
1.968 + this.prev = prev;
1.969 + }
1.970 + }
1.971 +
1.972 + /**
1.973 + * @since 1.6
1.974 + */
1.975 + public Iterator<E> descendingIterator() {
1.976 + return new DescendingIterator();
1.977 + }
1.978 +
1.979 + /**
1.980 + * Adapter to provide descending iterators via ListItr.previous
1.981 + */
1.982 + private class DescendingIterator implements Iterator<E> {
1.983 + private final ListItr itr = new ListItr(size());
1.984 + public boolean hasNext() {
1.985 + return itr.hasPrevious();
1.986 + }
1.987 + public E next() {
1.988 + return itr.previous();
1.989 + }
1.990 + public void remove() {
1.991 + itr.remove();
1.992 + }
1.993 + }
1.994 +
1.995 + @SuppressWarnings("unchecked")
1.996 + private LinkedList<E> superClone() {
1.997 + try {
1.998 + return (LinkedList<E>) super.clone();
1.999 + } catch (CloneNotSupportedException e) {
1.1000 + throw new InternalError();
1.1001 + }
1.1002 + }
1.1003 +
1.1004 + /**
1.1005 + * Returns a shallow copy of this {@code LinkedList}. (The elements
1.1006 + * themselves are not cloned.)
1.1007 + *
1.1008 + * @return a shallow copy of this {@code LinkedList} instance
1.1009 + */
1.1010 + public Object clone() {
1.1011 + LinkedList<E> clone = superClone();
1.1012 +
1.1013 + // Put clone into "virgin" state
1.1014 + clone.first = clone.last = null;
1.1015 + clone.size = 0;
1.1016 + clone.modCount = 0;
1.1017 +
1.1018 + // Initialize clone with our elements
1.1019 + for (Node<E> x = first; x != null; x = x.next)
1.1020 + clone.add(x.item);
1.1021 +
1.1022 + return clone;
1.1023 + }
1.1024 +
1.1025 + /**
1.1026 + * Returns an array containing all of the elements in this list
1.1027 + * in proper sequence (from first to last element).
1.1028 + *
1.1029 + * <p>The returned array will be "safe" in that no references to it are
1.1030 + * maintained by this list. (In other words, this method must allocate
1.1031 + * a new array). The caller is thus free to modify the returned array.
1.1032 + *
1.1033 + * <p>This method acts as bridge between array-based and collection-based
1.1034 + * APIs.
1.1035 + *
1.1036 + * @return an array containing all of the elements in this list
1.1037 + * in proper sequence
1.1038 + */
1.1039 + public Object[] toArray() {
1.1040 + Object[] result = new Object[size];
1.1041 + int i = 0;
1.1042 + for (Node<E> x = first; x != null; x = x.next)
1.1043 + result[i++] = x.item;
1.1044 + return result;
1.1045 + }
1.1046 +
1.1047 + /**
1.1048 + * Returns an array containing all of the elements in this list in
1.1049 + * proper sequence (from first to last element); the runtime type of
1.1050 + * the returned array is that of the specified array. If the list fits
1.1051 + * in the specified array, it is returned therein. Otherwise, a new
1.1052 + * array is allocated with the runtime type of the specified array and
1.1053 + * the size of this list.
1.1054 + *
1.1055 + * <p>If the list fits in the specified array with room to spare (i.e.,
1.1056 + * the array has more elements than the list), the element in the array
1.1057 + * immediately following the end of the list is set to {@code null}.
1.1058 + * (This is useful in determining the length of the list <i>only</i> if
1.1059 + * the caller knows that the list does not contain any null elements.)
1.1060 + *
1.1061 + * <p>Like the {@link #toArray()} method, this method acts as bridge between
1.1062 + * array-based and collection-based APIs. Further, this method allows
1.1063 + * precise control over the runtime type of the output array, and may,
1.1064 + * under certain circumstances, be used to save allocation costs.
1.1065 + *
1.1066 + * <p>Suppose {@code x} is a list known to contain only strings.
1.1067 + * The following code can be used to dump the list into a newly
1.1068 + * allocated array of {@code String}:
1.1069 + *
1.1070 + * <pre>
1.1071 + * String[] y = x.toArray(new String[0]);</pre>
1.1072 + *
1.1073 + * Note that {@code toArray(new Object[0])} is identical in function to
1.1074 + * {@code toArray()}.
1.1075 + *
1.1076 + * @param a the array into which the elements of the list are to
1.1077 + * be stored, if it is big enough; otherwise, a new array of the
1.1078 + * same runtime type is allocated for this purpose.
1.1079 + * @return an array containing the elements of the list
1.1080 + * @throws ArrayStoreException if the runtime type of the specified array
1.1081 + * is not a supertype of the runtime type of every element in
1.1082 + * this list
1.1083 + * @throws NullPointerException if the specified array is null
1.1084 + */
1.1085 + @SuppressWarnings("unchecked")
1.1086 + public <T> T[] toArray(T[] a) {
1.1087 + if (a.length < size)
1.1088 + a = (T[])java.lang.reflect.Array.newInstance(
1.1089 + a.getClass().getComponentType(), size);
1.1090 + int i = 0;
1.1091 + Object[] result = a;
1.1092 + for (Node<E> x = first; x != null; x = x.next)
1.1093 + result[i++] = x.item;
1.1094 +
1.1095 + if (a.length > size)
1.1096 + a[size] = null;
1.1097 +
1.1098 + return a;
1.1099 + }
1.1100 +
1.1101 + private static final long serialVersionUID = 876323262645176354L;
1.1102 +
1.1103 +}