jaroslav@597: /*
jaroslav@597: * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
jaroslav@597: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
jaroslav@597: *
jaroslav@597: * This code is free software; you can redistribute it and/or modify it
jaroslav@597: * under the terms of the GNU General Public License version 2 only, as
jaroslav@597: * published by the Free Software Foundation. Oracle designates this
jaroslav@597: * particular file as subject to the "Classpath" exception as provided
jaroslav@597: * by Oracle in the LICENSE file that accompanied this code.
jaroslav@597: *
jaroslav@597: * This code is distributed in the hope that it will be useful, but WITHOUT
jaroslav@597: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
jaroslav@597: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
jaroslav@597: * version 2 for more details (a copy is included in the LICENSE file that
jaroslav@597: * accompanied this code).
jaroslav@597: *
jaroslav@597: * You should have received a copy of the GNU General Public License version
jaroslav@597: * 2 along with this work; if not, write to the Free Software Foundation,
jaroslav@597: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
jaroslav@597: *
jaroslav@597: * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
jaroslav@597: * or visit www.oracle.com if you need additional information or have any
jaroslav@597: * questions.
jaroslav@597: */
jaroslav@597:
jaroslav@597: package java.util;
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Doubly-linked list implementation of the {@code List} and {@code Deque}
jaroslav@597: * interfaces. Implements all optional list operations, and permits all
jaroslav@597: * elements (including {@code null}).
jaroslav@597: *
jaroslav@597: * All of the operations perform as could be expected for a doubly-linked
jaroslav@597: * list. Operations that index into the list will traverse the list from
jaroslav@597: * the beginning or the end, whichever is closer to the specified index.
jaroslav@597: *
jaroslav@597: *
Note that this implementation is not synchronized.
jaroslav@597: * If multiple threads access a linked list concurrently, and at least
jaroslav@597: * one of the threads modifies the list structurally, it must be
jaroslav@597: * synchronized externally. (A structural modification is any operation
jaroslav@597: * that adds or deletes one or more elements; merely setting the value of
jaroslav@597: * an element is not a structural modification.) This is typically
jaroslav@597: * accomplished by synchronizing on some object that naturally
jaroslav@597: * encapsulates the list.
jaroslav@597: *
jaroslav@597: * If no such object exists, the list should be "wrapped" using the
jaroslav@597: * {@link Collections#synchronizedList Collections.synchronizedList}
jaroslav@597: * method. This is best done at creation time, to prevent accidental
jaroslav@597: * unsynchronized access to the list:
jaroslav@597: * List list = Collections.synchronizedList(new LinkedList(...));
jaroslav@597: *
jaroslav@597: * The iterators returned by this class's {@code iterator} and
jaroslav@597: * {@code listIterator} methods are fail-fast: if the list is
jaroslav@597: * structurally modified at any time after the iterator is created, in
jaroslav@597: * any way except through the Iterator's own {@code remove} or
jaroslav@597: * {@code add} methods, the iterator will throw a {@link
jaroslav@597: * ConcurrentModificationException}. Thus, in the face of concurrent
jaroslav@597: * modification, the iterator fails quickly and cleanly, rather than
jaroslav@597: * risking arbitrary, non-deterministic behavior at an undetermined
jaroslav@597: * time in the future.
jaroslav@597: *
jaroslav@597: *
Note that the fail-fast behavior of an iterator cannot be guaranteed
jaroslav@597: * as it is, generally speaking, impossible to make any hard guarantees in the
jaroslav@597: * presence of unsynchronized concurrent modification. Fail-fast iterators
jaroslav@597: * throw {@code ConcurrentModificationException} on a best-effort basis.
jaroslav@597: * Therefore, it would be wrong to write a program that depended on this
jaroslav@597: * exception for its correctness: the fail-fast behavior of iterators
jaroslav@597: * should be used only to detect bugs.
jaroslav@597: *
jaroslav@597: *
This class is a member of the
jaroslav@597: *
jaroslav@597: * Java Collections Framework.
jaroslav@597: *
jaroslav@597: * @author Josh Bloch
jaroslav@597: * @see List
jaroslav@597: * @see ArrayList
jaroslav@597: * @since 1.2
jaroslav@597: * @param the type of elements held in this collection
jaroslav@597: */
jaroslav@597:
jaroslav@597: public class LinkedList
jaroslav@597: extends AbstractSequentialList
jaroslav@597: implements List, Deque, Cloneable, java.io.Serializable
jaroslav@597: {
jaroslav@597: transient int size = 0;
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Pointer to first node.
jaroslav@597: * Invariant: (first == null && last == null) ||
jaroslav@597: * (first.prev == null && first.item != null)
jaroslav@597: */
jaroslav@597: transient Node first;
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Pointer to last node.
jaroslav@597: * Invariant: (first == null && last == null) ||
jaroslav@597: * (last.next == null && last.item != null)
jaroslav@597: */
jaroslav@597: transient Node last;
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Constructs an empty list.
jaroslav@597: */
jaroslav@597: public LinkedList() {
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Constructs a list containing the elements of the specified
jaroslav@597: * collection, in the order they are returned by the collection's
jaroslav@597: * iterator.
jaroslav@597: *
jaroslav@597: * @param c the collection whose elements are to be placed into this list
jaroslav@597: * @throws NullPointerException if the specified collection is null
jaroslav@597: */
jaroslav@597: public LinkedList(Collection c) {
jaroslav@597: this();
jaroslav@597: addAll(c);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Links e as first element.
jaroslav@597: */
jaroslav@597: private void linkFirst(E e) {
jaroslav@597: final Node f = first;
jaroslav@597: final Node newNode = new Node<>(null, e, f);
jaroslav@597: first = newNode;
jaroslav@597: if (f == null)
jaroslav@597: last = newNode;
jaroslav@597: else
jaroslav@597: f.prev = newNode;
jaroslav@597: size++;
jaroslav@597: modCount++;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Links e as last element.
jaroslav@597: */
jaroslav@597: void linkLast(E e) {
jaroslav@597: final Node l = last;
jaroslav@597: final Node newNode = new Node<>(l, e, null);
jaroslav@597: last = newNode;
jaroslav@597: if (l == null)
jaroslav@597: first = newNode;
jaroslav@597: else
jaroslav@597: l.next = newNode;
jaroslav@597: size++;
jaroslav@597: modCount++;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Inserts element e before non-null Node succ.
jaroslav@597: */
jaroslav@597: void linkBefore(E e, Node succ) {
jaroslav@597: // assert succ != null;
jaroslav@597: final Node pred = succ.prev;
jaroslav@597: final Node newNode = new Node<>(pred, e, succ);
jaroslav@597: succ.prev = newNode;
jaroslav@597: if (pred == null)
jaroslav@597: first = newNode;
jaroslav@597: else
jaroslav@597: pred.next = newNode;
jaroslav@597: size++;
jaroslav@597: modCount++;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Unlinks non-null first node f.
jaroslav@597: */
jaroslav@597: private E unlinkFirst(Node f) {
jaroslav@597: // assert f == first && f != null;
jaroslav@597: final E element = f.item;
jaroslav@597: final Node next = f.next;
jaroslav@597: f.item = null;
jaroslav@597: f.next = null; // help GC
jaroslav@597: first = next;
jaroslav@597: if (next == null)
jaroslav@597: last = null;
jaroslav@597: else
jaroslav@597: next.prev = null;
jaroslav@597: size--;
jaroslav@597: modCount++;
jaroslav@597: return element;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Unlinks non-null last node l.
jaroslav@597: */
jaroslav@597: private E unlinkLast(Node l) {
jaroslav@597: // assert l == last && l != null;
jaroslav@597: final E element = l.item;
jaroslav@597: final Node prev = l.prev;
jaroslav@597: l.item = null;
jaroslav@597: l.prev = null; // help GC
jaroslav@597: last = prev;
jaroslav@597: if (prev == null)
jaroslav@597: first = null;
jaroslav@597: else
jaroslav@597: prev.next = null;
jaroslav@597: size--;
jaroslav@597: modCount++;
jaroslav@597: return element;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Unlinks non-null node x.
jaroslav@597: */
jaroslav@597: E unlink(Node x) {
jaroslav@597: // assert x != null;
jaroslav@597: final E element = x.item;
jaroslav@597: final Node next = x.next;
jaroslav@597: final Node prev = x.prev;
jaroslav@597:
jaroslav@597: if (prev == null) {
jaroslav@597: first = next;
jaroslav@597: } else {
jaroslav@597: prev.next = next;
jaroslav@597: x.prev = null;
jaroslav@597: }
jaroslav@597:
jaroslav@597: if (next == null) {
jaroslav@597: last = prev;
jaroslav@597: } else {
jaroslav@597: next.prev = prev;
jaroslav@597: x.next = null;
jaroslav@597: }
jaroslav@597:
jaroslav@597: x.item = null;
jaroslav@597: size--;
jaroslav@597: modCount++;
jaroslav@597: return element;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns the first element in this list.
jaroslav@597: *
jaroslav@597: * @return the first element in this list
jaroslav@597: * @throws NoSuchElementException if this list is empty
jaroslav@597: */
jaroslav@597: public E getFirst() {
jaroslav@597: final Node f = first;
jaroslav@597: if (f == null)
jaroslav@597: throw new NoSuchElementException();
jaroslav@597: return f.item;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns the last element in this list.
jaroslav@597: *
jaroslav@597: * @return the last element in this list
jaroslav@597: * @throws NoSuchElementException if this list is empty
jaroslav@597: */
jaroslav@597: public E getLast() {
jaroslav@597: final Node l = last;
jaroslav@597: if (l == null)
jaroslav@597: throw new NoSuchElementException();
jaroslav@597: return l.item;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Removes and returns the first element from this list.
jaroslav@597: *
jaroslav@597: * @return the first element from this list
jaroslav@597: * @throws NoSuchElementException if this list is empty
jaroslav@597: */
jaroslav@597: public E removeFirst() {
jaroslav@597: final Node f = first;
jaroslav@597: if (f == null)
jaroslav@597: throw new NoSuchElementException();
jaroslav@597: return unlinkFirst(f);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Removes and returns the last element from this list.
jaroslav@597: *
jaroslav@597: * @return the last element from this list
jaroslav@597: * @throws NoSuchElementException if this list is empty
jaroslav@597: */
jaroslav@597: public E removeLast() {
jaroslav@597: final Node l = last;
jaroslav@597: if (l == null)
jaroslav@597: throw new NoSuchElementException();
jaroslav@597: return unlinkLast(l);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Inserts the specified element at the beginning of this list.
jaroslav@597: *
jaroslav@597: * @param e the element to add
jaroslav@597: */
jaroslav@597: public void addFirst(E e) {
jaroslav@597: linkFirst(e);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Appends the specified element to the end of this list.
jaroslav@597: *
jaroslav@597: * This method is equivalent to {@link #add}.
jaroslav@597: *
jaroslav@597: * @param e the element to add
jaroslav@597: */
jaroslav@597: public void addLast(E e) {
jaroslav@597: linkLast(e);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns {@code true} if this list contains the specified element.
jaroslav@597: * More formally, returns {@code true} if and only if this list contains
jaroslav@597: * at least one element {@code e} such that
jaroslav@597: * (o==null ? e==null : o.equals(e)).
jaroslav@597: *
jaroslav@597: * @param o element whose presence in this list is to be tested
jaroslav@597: * @return {@code true} if this list contains the specified element
jaroslav@597: */
jaroslav@597: public boolean contains(Object o) {
jaroslav@597: return indexOf(o) != -1;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns the number of elements in this list.
jaroslav@597: *
jaroslav@597: * @return the number of elements in this list
jaroslav@597: */
jaroslav@597: public int size() {
jaroslav@597: return size;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Appends the specified element to the end of this list.
jaroslav@597: *
jaroslav@597: *
This method is equivalent to {@link #addLast}.
jaroslav@597: *
jaroslav@597: * @param e element to be appended to this list
jaroslav@597: * @return {@code true} (as specified by {@link Collection#add})
jaroslav@597: */
jaroslav@597: public boolean add(E e) {
jaroslav@597: linkLast(e);
jaroslav@597: return true;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Removes the first occurrence of the specified element from this list,
jaroslav@597: * if it is present. If this list does not contain the element, it is
jaroslav@597: * unchanged. More formally, removes the element with the lowest index
jaroslav@597: * {@code i} such that
jaroslav@597: * (o==null ? get(i)==null : o.equals(get(i)))
jaroslav@597: * (if such an element exists). Returns {@code true} if this list
jaroslav@597: * contained the specified element (or equivalently, if this list
jaroslav@597: * changed as a result of the call).
jaroslav@597: *
jaroslav@597: * @param o element to be removed from this list, if present
jaroslav@597: * @return {@code true} if this list contained the specified element
jaroslav@597: */
jaroslav@597: public boolean remove(Object o) {
jaroslav@597: if (o == null) {
jaroslav@597: for (Node x = first; x != null; x = x.next) {
jaroslav@597: if (x.item == null) {
jaroslav@597: unlink(x);
jaroslav@597: return true;
jaroslav@597: }
jaroslav@597: }
jaroslav@597: } else {
jaroslav@597: for (Node x = first; x != null; x = x.next) {
jaroslav@597: if (o.equals(x.item)) {
jaroslav@597: unlink(x);
jaroslav@597: return true;
jaroslav@597: }
jaroslav@597: }
jaroslav@597: }
jaroslav@597: return false;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Appends all of the elements in the specified collection to the end of
jaroslav@597: * this list, in the order that they are returned by the specified
jaroslav@597: * collection's iterator. The behavior of this operation is undefined if
jaroslav@597: * the specified collection is modified while the operation is in
jaroslav@597: * progress. (Note that this will occur if the specified collection is
jaroslav@597: * this list, and it's nonempty.)
jaroslav@597: *
jaroslav@597: * @param c collection containing elements to be added to this list
jaroslav@597: * @return {@code true} if this list changed as a result of the call
jaroslav@597: * @throws NullPointerException if the specified collection is null
jaroslav@597: */
jaroslav@597: public boolean addAll(Collection c) {
jaroslav@597: return addAll(size, c);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Inserts all of the elements in the specified collection into this
jaroslav@597: * list, starting at the specified position. Shifts the element
jaroslav@597: * currently at that position (if any) and any subsequent elements to
jaroslav@597: * the right (increases their indices). The new elements will appear
jaroslav@597: * in the list in the order that they are returned by the
jaroslav@597: * specified collection's iterator.
jaroslav@597: *
jaroslav@597: * @param index index at which to insert the first element
jaroslav@597: * from the specified collection
jaroslav@597: * @param c collection containing elements to be added to this list
jaroslav@597: * @return {@code true} if this list changed as a result of the call
jaroslav@597: * @throws IndexOutOfBoundsException {@inheritDoc}
jaroslav@597: * @throws NullPointerException if the specified collection is null
jaroslav@597: */
jaroslav@597: public boolean addAll(int index, Collection c) {
jaroslav@597: checkPositionIndex(index);
jaroslav@597:
jaroslav@597: Object[] a = c.toArray();
jaroslav@597: int numNew = a.length;
jaroslav@597: if (numNew == 0)
jaroslav@597: return false;
jaroslav@597:
jaroslav@597: Node pred, succ;
jaroslav@597: if (index == size) {
jaroslav@597: succ = null;
jaroslav@597: pred = last;
jaroslav@597: } else {
jaroslav@597: succ = node(index);
jaroslav@597: pred = succ.prev;
jaroslav@597: }
jaroslav@597:
jaroslav@597: for (Object o : a) {
jaroslav@597: @SuppressWarnings("unchecked") E e = (E) o;
jaroslav@597: Node newNode = new Node<>(pred, e, null);
jaroslav@597: if (pred == null)
jaroslav@597: first = newNode;
jaroslav@597: else
jaroslav@597: pred.next = newNode;
jaroslav@597: pred = newNode;
jaroslav@597: }
jaroslav@597:
jaroslav@597: if (succ == null) {
jaroslav@597: last = pred;
jaroslav@597: } else {
jaroslav@597: pred.next = succ;
jaroslav@597: succ.prev = pred;
jaroslav@597: }
jaroslav@597:
jaroslav@597: size += numNew;
jaroslav@597: modCount++;
jaroslav@597: return true;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Removes all of the elements from this list.
jaroslav@597: * The list will be empty after this call returns.
jaroslav@597: */
jaroslav@597: public void clear() {
jaroslav@597: // Clearing all of the links between nodes is "unnecessary", but:
jaroslav@597: // - helps a generational GC if the discarded nodes inhabit
jaroslav@597: // more than one generation
jaroslav@597: // - is sure to free memory even if there is a reachable Iterator
jaroslav@597: for (Node x = first; x != null; ) {
jaroslav@597: Node next = x.next;
jaroslav@597: x.item = null;
jaroslav@597: x.next = null;
jaroslav@597: x.prev = null;
jaroslav@597: x = next;
jaroslav@597: }
jaroslav@597: first = last = null;
jaroslav@597: size = 0;
jaroslav@597: modCount++;
jaroslav@597: }
jaroslav@597:
jaroslav@597:
jaroslav@597: // Positional Access Operations
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns the element at the specified position in this list.
jaroslav@597: *
jaroslav@597: * @param index index of the element to return
jaroslav@597: * @return the element at the specified position in this list
jaroslav@597: * @throws IndexOutOfBoundsException {@inheritDoc}
jaroslav@597: */
jaroslav@597: public E get(int index) {
jaroslav@597: checkElementIndex(index);
jaroslav@597: return node(index).item;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Replaces the element at the specified position in this list with the
jaroslav@597: * specified element.
jaroslav@597: *
jaroslav@597: * @param index index of the element to replace
jaroslav@597: * @param element element to be stored at the specified position
jaroslav@597: * @return the element previously at the specified position
jaroslav@597: * @throws IndexOutOfBoundsException {@inheritDoc}
jaroslav@597: */
jaroslav@597: public E set(int index, E element) {
jaroslav@597: checkElementIndex(index);
jaroslav@597: Node x = node(index);
jaroslav@597: E oldVal = x.item;
jaroslav@597: x.item = element;
jaroslav@597: return oldVal;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Inserts the specified element at the specified position in this list.
jaroslav@597: * Shifts the element currently at that position (if any) and any
jaroslav@597: * subsequent elements to the right (adds one to their indices).
jaroslav@597: *
jaroslav@597: * @param index index at which the specified element is to be inserted
jaroslav@597: * @param element element to be inserted
jaroslav@597: * @throws IndexOutOfBoundsException {@inheritDoc}
jaroslav@597: */
jaroslav@597: public void add(int index, E element) {
jaroslav@597: checkPositionIndex(index);
jaroslav@597:
jaroslav@597: if (index == size)
jaroslav@597: linkLast(element);
jaroslav@597: else
jaroslav@597: linkBefore(element, node(index));
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Removes the element at the specified position in this list. Shifts any
jaroslav@597: * subsequent elements to the left (subtracts one from their indices).
jaroslav@597: * Returns the element that was removed from the list.
jaroslav@597: *
jaroslav@597: * @param index the index of the element to be removed
jaroslav@597: * @return the element previously at the specified position
jaroslav@597: * @throws IndexOutOfBoundsException {@inheritDoc}
jaroslav@597: */
jaroslav@597: public E remove(int index) {
jaroslav@597: checkElementIndex(index);
jaroslav@597: return unlink(node(index));
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Tells if the argument is the index of an existing element.
jaroslav@597: */
jaroslav@597: private boolean isElementIndex(int index) {
jaroslav@597: return index >= 0 && index < size;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Tells if the argument is the index of a valid position for an
jaroslav@597: * iterator or an add operation.
jaroslav@597: */
jaroslav@597: private boolean isPositionIndex(int index) {
jaroslav@597: return index >= 0 && index <= size;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Constructs an IndexOutOfBoundsException detail message.
jaroslav@597: * Of the many possible refactorings of the error handling code,
jaroslav@597: * this "outlining" performs best with both server and client VMs.
jaroslav@597: */
jaroslav@597: private String outOfBoundsMsg(int index) {
jaroslav@597: return "Index: "+index+", Size: "+size;
jaroslav@597: }
jaroslav@597:
jaroslav@597: private void checkElementIndex(int index) {
jaroslav@597: if (!isElementIndex(index))
jaroslav@597: throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
jaroslav@597: }
jaroslav@597:
jaroslav@597: private void checkPositionIndex(int index) {
jaroslav@597: if (!isPositionIndex(index))
jaroslav@597: throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns the (non-null) Node at the specified element index.
jaroslav@597: */
jaroslav@597: Node node(int index) {
jaroslav@597: // assert isElementIndex(index);
jaroslav@597:
jaroslav@597: if (index < (size >> 1)) {
jaroslav@597: Node x = first;
jaroslav@597: for (int i = 0; i < index; i++)
jaroslav@597: x = x.next;
jaroslav@597: return x;
jaroslav@597: } else {
jaroslav@597: Node x = last;
jaroslav@597: for (int i = size - 1; i > index; i--)
jaroslav@597: x = x.prev;
jaroslav@597: return x;
jaroslav@597: }
jaroslav@597: }
jaroslav@597:
jaroslav@597: // Search Operations
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns the index of the first occurrence of the specified element
jaroslav@597: * in this list, or -1 if this list does not contain the element.
jaroslav@597: * More formally, returns the lowest index {@code i} such that
jaroslav@597: * (o==null ? get(i)==null : o.equals(get(i))),
jaroslav@597: * or -1 if there is no such index.
jaroslav@597: *
jaroslav@597: * @param o element to search for
jaroslav@597: * @return the index of the first occurrence of the specified element in
jaroslav@597: * this list, or -1 if this list does not contain the element
jaroslav@597: */
jaroslav@597: public int indexOf(Object o) {
jaroslav@597: int index = 0;
jaroslav@597: if (o == null) {
jaroslav@597: for (Node x = first; x != null; x = x.next) {
jaroslav@597: if (x.item == null)
jaroslav@597: return index;
jaroslav@597: index++;
jaroslav@597: }
jaroslav@597: } else {
jaroslav@597: for (Node x = first; x != null; x = x.next) {
jaroslav@597: if (o.equals(x.item))
jaroslav@597: return index;
jaroslav@597: index++;
jaroslav@597: }
jaroslav@597: }
jaroslav@597: return -1;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns the index of the last occurrence of the specified element
jaroslav@597: * in this list, or -1 if this list does not contain the element.
jaroslav@597: * More formally, returns the highest index {@code i} such that
jaroslav@597: * (o==null ? get(i)==null : o.equals(get(i))),
jaroslav@597: * or -1 if there is no such index.
jaroslav@597: *
jaroslav@597: * @param o element to search for
jaroslav@597: * @return the index of the last occurrence of the specified element in
jaroslav@597: * this list, or -1 if this list does not contain the element
jaroslav@597: */
jaroslav@597: public int lastIndexOf(Object o) {
jaroslav@597: int index = size;
jaroslav@597: if (o == null) {
jaroslav@597: for (Node x = last; x != null; x = x.prev) {
jaroslav@597: index--;
jaroslav@597: if (x.item == null)
jaroslav@597: return index;
jaroslav@597: }
jaroslav@597: } else {
jaroslav@597: for (Node x = last; x != null; x = x.prev) {
jaroslav@597: index--;
jaroslav@597: if (o.equals(x.item))
jaroslav@597: return index;
jaroslav@597: }
jaroslav@597: }
jaroslav@597: return -1;
jaroslav@597: }
jaroslav@597:
jaroslav@597: // Queue operations.
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Retrieves, but does not remove, the head (first element) of this list.
jaroslav@597: *
jaroslav@597: * @return the head of this list, or {@code null} if this list is empty
jaroslav@597: * @since 1.5
jaroslav@597: */
jaroslav@597: public E peek() {
jaroslav@597: final Node f = first;
jaroslav@597: return (f == null) ? null : f.item;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Retrieves, but does not remove, the head (first element) of this list.
jaroslav@597: *
jaroslav@597: * @return the head of this list
jaroslav@597: * @throws NoSuchElementException if this list is empty
jaroslav@597: * @since 1.5
jaroslav@597: */
jaroslav@597: public E element() {
jaroslav@597: return getFirst();
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Retrieves and removes the head (first element) of this list.
jaroslav@597: *
jaroslav@597: * @return the head of this list, or {@code null} if this list is empty
jaroslav@597: * @since 1.5
jaroslav@597: */
jaroslav@597: public E poll() {
jaroslav@597: final Node f = first;
jaroslav@597: return (f == null) ? null : unlinkFirst(f);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Retrieves and removes the head (first element) of this list.
jaroslav@597: *
jaroslav@597: * @return the head of this list
jaroslav@597: * @throws NoSuchElementException if this list is empty
jaroslav@597: * @since 1.5
jaroslav@597: */
jaroslav@597: public E remove() {
jaroslav@597: return removeFirst();
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Adds the specified element as the tail (last element) of this list.
jaroslav@597: *
jaroslav@597: * @param e the element to add
jaroslav@597: * @return {@code true} (as specified by {@link Queue#offer})
jaroslav@597: * @since 1.5
jaroslav@597: */
jaroslav@597: public boolean offer(E e) {
jaroslav@597: return add(e);
jaroslav@597: }
jaroslav@597:
jaroslav@597: // Deque operations
jaroslav@597: /**
jaroslav@597: * Inserts the specified element at the front of this list.
jaroslav@597: *
jaroslav@597: * @param e the element to insert
jaroslav@597: * @return {@code true} (as specified by {@link Deque#offerFirst})
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public boolean offerFirst(E e) {
jaroslav@597: addFirst(e);
jaroslav@597: return true;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Inserts the specified element at the end of this list.
jaroslav@597: *
jaroslav@597: * @param e the element to insert
jaroslav@597: * @return {@code true} (as specified by {@link Deque#offerLast})
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public boolean offerLast(E e) {
jaroslav@597: addLast(e);
jaroslav@597: return true;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Retrieves, but does not remove, the first element of this list,
jaroslav@597: * or returns {@code null} if this list is empty.
jaroslav@597: *
jaroslav@597: * @return the first element of this list, or {@code null}
jaroslav@597: * if this list is empty
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public E peekFirst() {
jaroslav@597: final Node f = first;
jaroslav@597: return (f == null) ? null : f.item;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Retrieves, but does not remove, the last element of this list,
jaroslav@597: * or returns {@code null} if this list is empty.
jaroslav@597: *
jaroslav@597: * @return the last element of this list, or {@code null}
jaroslav@597: * if this list is empty
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public E peekLast() {
jaroslav@597: final Node l = last;
jaroslav@597: return (l == null) ? null : l.item;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Retrieves and removes the first element of this list,
jaroslav@597: * or returns {@code null} if this list is empty.
jaroslav@597: *
jaroslav@597: * @return the first element of this list, or {@code null} if
jaroslav@597: * this list is empty
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public E pollFirst() {
jaroslav@597: final Node f = first;
jaroslav@597: return (f == null) ? null : unlinkFirst(f);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Retrieves and removes the last element of this list,
jaroslav@597: * or returns {@code null} if this list is empty.
jaroslav@597: *
jaroslav@597: * @return the last element of this list, or {@code null} if
jaroslav@597: * this list is empty
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public E pollLast() {
jaroslav@597: final Node l = last;
jaroslav@597: return (l == null) ? null : unlinkLast(l);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Pushes an element onto the stack represented by this list. In other
jaroslav@597: * words, inserts the element at the front of this list.
jaroslav@597: *
jaroslav@597: * This method is equivalent to {@link #addFirst}.
jaroslav@597: *
jaroslav@597: * @param e the element to push
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public void push(E e) {
jaroslav@597: addFirst(e);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Pops an element from the stack represented by this list. In other
jaroslav@597: * words, removes and returns the first element of this list.
jaroslav@597: *
jaroslav@597: *
This method is equivalent to {@link #removeFirst()}.
jaroslav@597: *
jaroslav@597: * @return the element at the front of this list (which is the top
jaroslav@597: * of the stack represented by this list)
jaroslav@597: * @throws NoSuchElementException if this list is empty
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public E pop() {
jaroslav@597: return removeFirst();
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Removes the first occurrence of the specified element in this
jaroslav@597: * list (when traversing the list from head to tail). If the list
jaroslav@597: * does not contain the element, it is unchanged.
jaroslav@597: *
jaroslav@597: * @param o element to be removed from this list, if present
jaroslav@597: * @return {@code true} if the list contained the specified element
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public boolean removeFirstOccurrence(Object o) {
jaroslav@597: return remove(o);
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Removes the last occurrence of the specified element in this
jaroslav@597: * list (when traversing the list from head to tail). If the list
jaroslav@597: * does not contain the element, it is unchanged.
jaroslav@597: *
jaroslav@597: * @param o element to be removed from this list, if present
jaroslav@597: * @return {@code true} if the list contained the specified element
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public boolean removeLastOccurrence(Object o) {
jaroslav@597: if (o == null) {
jaroslav@597: for (Node x = last; x != null; x = x.prev) {
jaroslav@597: if (x.item == null) {
jaroslav@597: unlink(x);
jaroslav@597: return true;
jaroslav@597: }
jaroslav@597: }
jaroslav@597: } else {
jaroslav@597: for (Node x = last; x != null; x = x.prev) {
jaroslav@597: if (o.equals(x.item)) {
jaroslav@597: unlink(x);
jaroslav@597: return true;
jaroslav@597: }
jaroslav@597: }
jaroslav@597: }
jaroslav@597: return false;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns a list-iterator of the elements in this list (in proper
jaroslav@597: * sequence), starting at the specified position in the list.
jaroslav@597: * Obeys the general contract of {@code List.listIterator(int)}.
jaroslav@597: *
jaroslav@597: * The list-iterator is fail-fast: if the list is structurally
jaroslav@597: * modified at any time after the Iterator is created, in any way except
jaroslav@597: * through the list-iterator's own {@code remove} or {@code add}
jaroslav@597: * methods, the list-iterator will throw a
jaroslav@597: * {@code ConcurrentModificationException}. Thus, in the face of
jaroslav@597: * concurrent modification, the iterator fails quickly and cleanly, rather
jaroslav@597: * than risking arbitrary, non-deterministic behavior at an undetermined
jaroslav@597: * time in the future.
jaroslav@597: *
jaroslav@597: * @param index index of the first element to be returned from the
jaroslav@597: * list-iterator (by a call to {@code next})
jaroslav@597: * @return a ListIterator of the elements in this list (in proper
jaroslav@597: * sequence), starting at the specified position in the list
jaroslav@597: * @throws IndexOutOfBoundsException {@inheritDoc}
jaroslav@597: * @see List#listIterator(int)
jaroslav@597: */
jaroslav@597: public ListIterator listIterator(int index) {
jaroslav@597: checkPositionIndex(index);
jaroslav@597: return new ListItr(index);
jaroslav@597: }
jaroslav@597:
jaroslav@597: private class ListItr implements ListIterator {
jaroslav@597: private Node lastReturned = null;
jaroslav@597: private Node next;
jaroslav@597: private int nextIndex;
jaroslav@597: private int expectedModCount = modCount;
jaroslav@597:
jaroslav@597: ListItr(int index) {
jaroslav@597: // assert isPositionIndex(index);
jaroslav@597: next = (index == size) ? null : node(index);
jaroslav@597: nextIndex = index;
jaroslav@597: }
jaroslav@597:
jaroslav@597: public boolean hasNext() {
jaroslav@597: return nextIndex < size;
jaroslav@597: }
jaroslav@597:
jaroslav@597: public E next() {
jaroslav@597: checkForComodification();
jaroslav@597: if (!hasNext())
jaroslav@597: throw new NoSuchElementException();
jaroslav@597:
jaroslav@597: lastReturned = next;
jaroslav@597: next = next.next;
jaroslav@597: nextIndex++;
jaroslav@597: return lastReturned.item;
jaroslav@597: }
jaroslav@597:
jaroslav@597: public boolean hasPrevious() {
jaroslav@597: return nextIndex > 0;
jaroslav@597: }
jaroslav@597:
jaroslav@597: public E previous() {
jaroslav@597: checkForComodification();
jaroslav@597: if (!hasPrevious())
jaroslav@597: throw new NoSuchElementException();
jaroslav@597:
jaroslav@597: lastReturned = next = (next == null) ? last : next.prev;
jaroslav@597: nextIndex--;
jaroslav@597: return lastReturned.item;
jaroslav@597: }
jaroslav@597:
jaroslav@597: public int nextIndex() {
jaroslav@597: return nextIndex;
jaroslav@597: }
jaroslav@597:
jaroslav@597: public int previousIndex() {
jaroslav@597: return nextIndex - 1;
jaroslav@597: }
jaroslav@597:
jaroslav@597: public void remove() {
jaroslav@597: checkForComodification();
jaroslav@597: if (lastReturned == null)
jaroslav@597: throw new IllegalStateException();
jaroslav@597:
jaroslav@597: Node lastNext = lastReturned.next;
jaroslav@597: unlink(lastReturned);
jaroslav@597: if (next == lastReturned)
jaroslav@597: next = lastNext;
jaroslav@597: else
jaroslav@597: nextIndex--;
jaroslav@597: lastReturned = null;
jaroslav@597: expectedModCount++;
jaroslav@597: }
jaroslav@597:
jaroslav@597: public void set(E e) {
jaroslav@597: if (lastReturned == null)
jaroslav@597: throw new IllegalStateException();
jaroslav@597: checkForComodification();
jaroslav@597: lastReturned.item = e;
jaroslav@597: }
jaroslav@597:
jaroslav@597: public void add(E e) {
jaroslav@597: checkForComodification();
jaroslav@597: lastReturned = null;
jaroslav@597: if (next == null)
jaroslav@597: linkLast(e);
jaroslav@597: else
jaroslav@597: linkBefore(e, next);
jaroslav@597: nextIndex++;
jaroslav@597: expectedModCount++;
jaroslav@597: }
jaroslav@597:
jaroslav@597: final void checkForComodification() {
jaroslav@597: if (modCount != expectedModCount)
jaroslav@597: throw new ConcurrentModificationException();
jaroslav@597: }
jaroslav@597: }
jaroslav@597:
jaroslav@597: private static class Node {
jaroslav@597: E item;
jaroslav@597: Node next;
jaroslav@597: Node prev;
jaroslav@597:
jaroslav@597: Node(Node prev, E element, Node next) {
jaroslav@597: this.item = element;
jaroslav@597: this.next = next;
jaroslav@597: this.prev = prev;
jaroslav@597: }
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * @since 1.6
jaroslav@597: */
jaroslav@597: public Iterator descendingIterator() {
jaroslav@597: return new DescendingIterator();
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Adapter to provide descending iterators via ListItr.previous
jaroslav@597: */
jaroslav@597: private class DescendingIterator implements Iterator {
jaroslav@597: private final ListItr itr = new ListItr(size());
jaroslav@597: public boolean hasNext() {
jaroslav@597: return itr.hasPrevious();
jaroslav@597: }
jaroslav@597: public E next() {
jaroslav@597: return itr.previous();
jaroslav@597: }
jaroslav@597: public void remove() {
jaroslav@597: itr.remove();
jaroslav@597: }
jaroslav@597: }
jaroslav@597:
jaroslav@597: @SuppressWarnings("unchecked")
jaroslav@597: private LinkedList superClone() {
jaroslav@597: try {
jaroslav@597: return (LinkedList) super.clone();
jaroslav@597: } catch (CloneNotSupportedException e) {
jaroslav@597: throw new InternalError();
jaroslav@597: }
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns a shallow copy of this {@code LinkedList}. (The elements
jaroslav@597: * themselves are not cloned.)
jaroslav@597: *
jaroslav@597: * @return a shallow copy of this {@code LinkedList} instance
jaroslav@597: */
jaroslav@597: public Object clone() {
jaroslav@597: LinkedList clone = superClone();
jaroslav@597:
jaroslav@597: // Put clone into "virgin" state
jaroslav@597: clone.first = clone.last = null;
jaroslav@597: clone.size = 0;
jaroslav@597: clone.modCount = 0;
jaroslav@597:
jaroslav@597: // Initialize clone with our elements
jaroslav@597: for (Node x = first; x != null; x = x.next)
jaroslav@597: clone.add(x.item);
jaroslav@597:
jaroslav@597: return clone;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns an array containing all of the elements in this list
jaroslav@597: * in proper sequence (from first to last element).
jaroslav@597: *
jaroslav@597: * The returned array will be "safe" in that no references to it are
jaroslav@597: * maintained by this list. (In other words, this method must allocate
jaroslav@597: * a new array). The caller is thus free to modify the returned array.
jaroslav@597: *
jaroslav@597: *
This method acts as bridge between array-based and collection-based
jaroslav@597: * APIs.
jaroslav@597: *
jaroslav@597: * @return an array containing all of the elements in this list
jaroslav@597: * in proper sequence
jaroslav@597: */
jaroslav@597: public Object[] toArray() {
jaroslav@597: Object[] result = new Object[size];
jaroslav@597: int i = 0;
jaroslav@597: for (Node x = first; x != null; x = x.next)
jaroslav@597: result[i++] = x.item;
jaroslav@597: return result;
jaroslav@597: }
jaroslav@597:
jaroslav@597: /**
jaroslav@597: * Returns an array containing all of the elements in this list in
jaroslav@597: * proper sequence (from first to last element); the runtime type of
jaroslav@597: * the returned array is that of the specified array. If the list fits
jaroslav@597: * in the specified array, it is returned therein. Otherwise, a new
jaroslav@597: * array is allocated with the runtime type of the specified array and
jaroslav@597: * the size of this list.
jaroslav@597: *
jaroslav@597: * If the list fits in the specified array with room to spare (i.e.,
jaroslav@597: * the array has more elements than the list), the element in the array
jaroslav@597: * immediately following the end of the list is set to {@code null}.
jaroslav@597: * (This is useful in determining the length of the list only if
jaroslav@597: * the caller knows that the list does not contain any null elements.)
jaroslav@597: *
jaroslav@597: *
Like the {@link #toArray()} method, this method acts as bridge between
jaroslav@597: * array-based and collection-based APIs. Further, this method allows
jaroslav@597: * precise control over the runtime type of the output array, and may,
jaroslav@597: * under certain circumstances, be used to save allocation costs.
jaroslav@597: *
jaroslav@597: *
Suppose {@code x} is a list known to contain only strings.
jaroslav@597: * The following code can be used to dump the list into a newly
jaroslav@597: * allocated array of {@code String}:
jaroslav@597: *
jaroslav@597: *
jaroslav@597: * String[] y = x.toArray(new String[0]);
jaroslav@597: *
jaroslav@597: * Note that {@code toArray(new Object[0])} is identical in function to
jaroslav@597: * {@code toArray()}.
jaroslav@597: *
jaroslav@597: * @param a the array into which the elements of the list are to
jaroslav@597: * be stored, if it is big enough; otherwise, a new array of the
jaroslav@597: * same runtime type is allocated for this purpose.
jaroslav@597: * @return an array containing the elements of the list
jaroslav@597: * @throws ArrayStoreException if the runtime type of the specified array
jaroslav@597: * is not a supertype of the runtime type of every element in
jaroslav@597: * this list
jaroslav@597: * @throws NullPointerException if the specified array is null
jaroslav@597: */
jaroslav@597: @SuppressWarnings("unchecked")
jaroslav@597: public T[] toArray(T[] a) {
jaroslav@597: if (a.length < size)
jaroslav@597: a = (T[])java.lang.reflect.Array.newInstance(
jaroslav@597: a.getClass().getComponentType(), size);
jaroslav@597: int i = 0;
jaroslav@597: Object[] result = a;
jaroslav@597: for (Node x = first; x != null; x = x.next)
jaroslav@597: result[i++] = x.item;
jaroslav@597:
jaroslav@597: if (a.length > size)
jaroslav@597: a[size] = null;
jaroslav@597:
jaroslav@597: return a;
jaroslav@597: }
jaroslav@597:
jaroslav@597: private static final long serialVersionUID = 876323262645176354L;
jaroslav@597:
jaroslav@597: }