| /* |
| * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.util; |
| |
| import java.util.function.Consumer; |
| |
| /** |
| * Doubly-linked list implementation of the {@code List} and {@code Deque} |
| * interfaces. Implements all optional list operations, and permits all |
| * elements (including {@code null}). |
| * |
| * <p>All of the operations perform as could be expected for a doubly-linked |
| * list. Operations that index into the list will traverse the list from |
| * the beginning or the end, whichever is closer to the specified index. |
| * |
| * <p><strong>Note that this implementation is not synchronized.</strong> |
| * If multiple threads access a linked list concurrently, and at least |
| * one of the threads modifies the list structurally, it <i>must</i> be |
| * synchronized externally. (A structural modification is any operation |
| * that adds or deletes one or more elements; merely setting the value of |
| * an element is not a structural modification.) This is typically |
| * accomplished by synchronizing on some object that naturally |
| * encapsulates the list. |
| * |
| * If no such object exists, the list should be "wrapped" using the |
| * {@link Collections#synchronizedList Collections.synchronizedList} |
| * method. This is best done at creation time, to prevent accidental |
| * unsynchronized access to the list:<pre> |
| * List list = Collections.synchronizedList(new LinkedList(...));</pre> |
| * |
| * <p>The iterators returned by this class's {@code iterator} and |
| * {@code listIterator} methods are <i>fail-fast</i>: if the list is |
| * structurally modified at any time after the iterator is created, in |
| * any way except through the Iterator's own {@code remove} or |
| * {@code add} methods, the iterator will throw a {@link |
| * ConcurrentModificationException}. Thus, in the face of concurrent |
| * modification, the iterator fails quickly and cleanly, rather than |
| * risking arbitrary, non-deterministic behavior at an undetermined |
| * time in the future. |
| * |
| * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
| * as it is, generally speaking, impossible to make any hard guarantees in the |
| * presence of unsynchronized concurrent modification. Fail-fast iterators |
| * throw {@code ConcurrentModificationException} on a best-effort basis. |
| * Therefore, it would be wrong to write a program that depended on this |
| * exception for its correctness: <i>the fail-fast behavior of iterators |
| * should be used only to detect bugs.</i> |
| * |
| * <p>This class is a member of the |
| * <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/collections/index.html"> |
| * Java Collections Framework</a>. |
| * |
| * @author Josh Bloch |
| * @see List |
| * @see ArrayList |
| * @since 1.2 |
| * @param <E> the type of elements held in this collection |
| */ |
| |
| public class LinkedList<E> |
| extends AbstractSequentialList<E> |
| implements List<E>, Deque<E>, Cloneable, java.io.Serializable |
| { |
| transient int size = 0; |
| |
| /** |
| * Pointer to first node. |
| * Invariant: (first == null && last == null) || |
| * (first.prev == null && first.item != null) |
| */ |
| transient Node<E> first; |
| |
| /** |
| * Pointer to last node. |
| * Invariant: (first == null && last == null) || |
| * (last.next == null && last.item != null) |
| */ |
| transient Node<E> last; |
| |
| /** |
| * Constructs an empty list. |
| */ |
| public LinkedList() { |
| } |
| |
| /** |
| * Constructs a list containing the elements of the specified |
| * collection, in the order they are returned by the collection's |
| * iterator. |
| * |
| * @param c the collection whose elements are to be placed into this list |
| * @throws NullPointerException if the specified collection is null |
| */ |
| public LinkedList(Collection<? extends E> c) { |
| this(); |
| addAll(c); |
| } |
| |
| /** |
| * Links e as first element. |
| */ |
| private void linkFirst(E e) { |
| final Node<E> f = first; |
| final Node<E> newNode = new Node<>(null, e, f); |
| first = newNode; |
| if (f == null) |
| last = newNode; |
| else |
| f.prev = newNode; |
| size++; |
| modCount++; |
| } |
| |
| /** |
| * Links e as last element. |
| */ |
| void linkLast(E e) { |
| final Node<E> l = last; |
| final Node<E> newNode = new Node<>(l, e, null); |
| last = newNode; |
| if (l == null) |
| first = newNode; |
| else |
| l.next = newNode; |
| size++; |
| modCount++; |
| } |
| |
| /** |
| * Inserts element e before non-null Node succ. |
| */ |
| void linkBefore(E e, Node<E> succ) { |
| // assert succ != null; |
| final Node<E> pred = succ.prev; |
| final Node<E> newNode = new Node<>(pred, e, succ); |
| succ.prev = newNode; |
| if (pred == null) |
| first = newNode; |
| else |
| pred.next = newNode; |
| size++; |
| modCount++; |
| } |
| |
| /** |
| * Unlinks non-null first node f. |
| */ |
| private E unlinkFirst(Node<E> f) { |
| // assert f == first && f != null; |
| final E element = f.item; |
| final Node<E> next = f.next; |
| f.item = null; |
| f.next = null; // help GC |
| first = next; |
| if (next == null) |
| last = null; |
| else |
| next.prev = null; |
| size--; |
| modCount++; |
| return element; |
| } |
| |
| /** |
| * Unlinks non-null last node l. |
| */ |
| private E unlinkLast(Node<E> l) { |
| // assert l == last && l != null; |
| final E element = l.item; |
| final Node<E> prev = l.prev; |
| l.item = null; |
| l.prev = null; // help GC |
| last = prev; |
| if (prev == null) |
| first = null; |
| else |
| prev.next = null; |
| size--; |
| modCount++; |
| return element; |
| } |
| |
| /** |
| * Unlinks non-null node x. |
| */ |
| E unlink(Node<E> x) { |
| // assert x != null; |
| final E element = x.item; |
| final Node<E> next = x.next; |
| final Node<E> prev = x.prev; |
| |
| if (prev == null) { |
| first = next; |
| } else { |
| prev.next = next; |
| x.prev = null; |
| } |
| |
| if (next == null) { |
| last = prev; |
| } else { |
| next.prev = prev; |
| x.next = null; |
| } |
| |
| x.item = null; |
| size--; |
| modCount++; |
| return element; |
| } |
| |
| /** |
| * Returns the first element in this list. |
| * |
| * @return the first element in this list |
| * @throws NoSuchElementException if this list is empty |
| */ |
| public E getFirst() { |
| final Node<E> f = first; |
| if (f == null) |
| throw new NoSuchElementException(); |
| return f.item; |
| } |
| |
| /** |
| * Returns the last element in this list. |
| * |
| * @return the last element in this list |
| * @throws NoSuchElementException if this list is empty |
| */ |
| public E getLast() { |
| final Node<E> l = last; |
| if (l == null) |
| throw new NoSuchElementException(); |
| return l.item; |
| } |
| |
| /** |
| * Removes and returns the first element from this list. |
| * |
| * @return the first element from this list |
| * @throws NoSuchElementException if this list is empty |
| */ |
| public E removeFirst() { |
| final Node<E> f = first; |
| if (f == null) |
| throw new NoSuchElementException(); |
| return unlinkFirst(f); |
| } |
| |
| /** |
| * Removes and returns the last element from this list. |
| * |
| * @return the last element from this list |
| * @throws NoSuchElementException if this list is empty |
| */ |
| public E removeLast() { |
| final Node<E> l = last; |
| if (l == null) |
| throw new NoSuchElementException(); |
| return unlinkLast(l); |
| } |
| |
| /** |
| * Inserts the specified element at the beginning of this list. |
| * |
| * @param e the element to add |
| */ |
| public void addFirst(E e) { |
| linkFirst(e); |
| } |
| |
| /** |
| * Appends the specified element to the end of this list. |
| * |
| * <p>This method is equivalent to {@link #add}. |
| * |
| * @param e the element to add |
| */ |
| public void addLast(E e) { |
| linkLast(e); |
| } |
| |
| /** |
| * Returns {@code true} if this list contains the specified element. |
| * More formally, returns {@code true} if and only if this list contains |
| * at least one element {@code e} such that |
| * <tt>(o==null ? e==null : o.equals(e))</tt>. |
| * |
| * @param o element whose presence in this list is to be tested |
| * @return {@code true} if this list contains the specified element |
| */ |
| public boolean contains(Object o) { |
| return indexOf(o) != -1; |
| } |
| |
| /** |
| * Returns the number of elements in this list. |
| * |
| * @return the number of elements in this list |
| */ |
| public int size() { |
| return size; |
| } |
| |
| /** |
| * Appends the specified element to the end of this list. |
| * |
| * <p>This method is equivalent to {@link #addLast}. |
| * |
| * @param e element to be appended to this list |
| * @return {@code true} (as specified by {@link Collection#add}) |
| */ |
| public boolean add(E e) { |
| linkLast(e); |
| return true; |
| } |
| |
| /** |
| * Removes the first occurrence of the specified element from this list, |
| * if it is present. If this list does not contain the element, it is |
| * unchanged. More formally, removes the element with the lowest index |
| * {@code i} such that |
| * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> |
| * (if such an element exists). Returns {@code true} if this list |
| * contained the specified element (or equivalently, if this list |
| * changed as a result of the call). |
| * |
| * @param o element to be removed from this list, if present |
| * @return {@code true} if this list contained the specified element |
| */ |
| public boolean remove(Object o) { |
| if (o == null) { |
| for (Node<E> x = first; x != null; x = x.next) { |
| if (x.item == null) { |
| unlink(x); |
| return true; |
| } |
| } |
| } else { |
| for (Node<E> x = first; x != null; x = x.next) { |
| if (o.equals(x.item)) { |
| unlink(x); |
| return true; |
| } |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Appends all of the elements in the specified collection to the end of |
| * this list, in the order that they are returned by the specified |
| * collection's iterator. The behavior of this operation is undefined if |
| * the specified collection is modified while the operation is in |
| * progress. (Note that this will occur if the specified collection is |
| * this list, and it's nonempty.) |
| * |
| * @param c collection containing elements to be added to this list |
| * @return {@code true} if this list changed as a result of the call |
| * @throws NullPointerException if the specified collection is null |
| */ |
| public boolean addAll(Collection<? extends E> c) { |
| return addAll(size, c); |
| } |
| |
| /** |
| * Inserts all of the elements in the specified collection into this |
| * list, starting at the specified position. Shifts the element |
| * currently at that position (if any) and any subsequent elements to |
| * the right (increases their indices). The new elements will appear |
| * in the list in the order that they are returned by the |
| * specified collection's iterator. |
| * |
| * @param index index at which to insert the first element |
| * from the specified collection |
| * @param c collection containing elements to be added to this list |
| * @return {@code true} if this list changed as a result of the call |
| * @throws IndexOutOfBoundsException {@inheritDoc} |
| * @throws NullPointerException if the specified collection is null |
| */ |
| public boolean addAll(int index, Collection<? extends E> c) { |
| checkPositionIndex(index); |
| |
| Object[] a = c.toArray(); |
| int numNew = a.length; |
| if (numNew == 0) |
| return false; |
| |
| Node<E> pred, succ; |
| if (index == size) { |
| succ = null; |
| pred = last; |
| } else { |
| succ = node(index); |
| pred = succ.prev; |
| } |
| |
| for (Object o : a) { |
| @SuppressWarnings("unchecked") E e = (E) o; |
| Node<E> newNode = new Node<>(pred, e, null); |
| if (pred == null) |
| first = newNode; |
| else |
| pred.next = newNode; |
| pred = newNode; |
| } |
| |
| if (succ == null) { |
| last = pred; |
| } else { |
| pred.next = succ; |
| succ.prev = pred; |
| } |
| |
| size += numNew; |
| modCount++; |
| return true; |
| } |
| |
| /** |
| * Removes all of the elements from this list. |
| * The list will be empty after this call returns. |
| */ |
| public void clear() { |
| // Clearing all of the links between nodes is "unnecessary", but: |
| // - helps a generational GC if the discarded nodes inhabit |
| // more than one generation |
| // - is sure to free memory even if there is a reachable Iterator |
| for (Node<E> x = first; x != null; ) { |
| Node<E> next = x.next; |
| x.item = null; |
| x.next = null; |
| x.prev = null; |
| x = next; |
| } |
| first = last = null; |
| size = 0; |
| modCount++; |
| } |
| |
| |
| // Positional Access Operations |
| |
| /** |
| * Returns the element at the specified position in this list. |
| * |
| * @param index index of the element to return |
| * @return the element at the specified position in this list |
| * @throws IndexOutOfBoundsException {@inheritDoc} |
| */ |
| public E get(int index) { |
| checkElementIndex(index); |
| return node(index).item; |
| } |
| |
| /** |
| * Replaces the element at the specified position in this list with the |
| * specified element. |
| * |
| * @param index index of the element to replace |
| * @param element element to be stored at the specified position |
| * @return the element previously at the specified position |
| * @throws IndexOutOfBoundsException {@inheritDoc} |
| */ |
| public E set(int index, E element) { |
| checkElementIndex(index); |
| Node<E> x = node(index); |
| E oldVal = x.item; |
| x.item = element; |
| return oldVal; |
| } |
| |
| /** |
| * Inserts the specified element at the specified position in this list. |
| * Shifts the element currently at that position (if any) and any |
| * subsequent elements to the right (adds one to their indices). |
| * |
| * @param index index at which the specified element is to be inserted |
| * @param element element to be inserted |
| * @throws IndexOutOfBoundsException {@inheritDoc} |
| */ |
| public void add(int index, E element) { |
| checkPositionIndex(index); |
| |
| if (index == size) |
| linkLast(element); |
| else |
| linkBefore(element, node(index)); |
| } |
| |
| /** |
| * Removes the element at the specified position in this list. Shifts any |
| * subsequent elements to the left (subtracts one from their indices). |
| * Returns the element that was removed from the list. |
| * |
| * @param index the index of the element to be removed |
| * @return the element previously at the specified position |
| * @throws IndexOutOfBoundsException {@inheritDoc} |
| */ |
| public E remove(int index) { |
| checkElementIndex(index); |
| return unlink(node(index)); |
| } |
| |
| /** |
| * Tells if the argument is the index of an existing element. |
| */ |
| private boolean isElementIndex(int index) { |
| return index >= 0 && index < size; |
| } |
| |
| /** |
| * Tells if the argument is the index of a valid position for an |
| * iterator or an add operation. |
| */ |
| private boolean isPositionIndex(int index) { |
| return index >= 0 && index <= size; |
| } |
| |
| /** |
| * Constructs an IndexOutOfBoundsException detail message. |
| * Of the many possible refactorings of the error handling code, |
| * this "outlining" performs best with both server and client VMs. |
| */ |
| private String outOfBoundsMsg(int index) { |
| return "Index: "+index+", Size: "+size; |
| } |
| |
| private void checkElementIndex(int index) { |
| if (!isElementIndex(index)) |
| throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); |
| } |
| |
| private void checkPositionIndex(int index) { |
| if (!isPositionIndex(index)) |
| throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); |
| } |
| |
| /** |
| * Returns the (non-null) Node at the specified element index. |
| */ |
| Node<E> node(int index) { |
| // assert isElementIndex(index); |
| |
| if (index < (size >> 1)) { |
| Node<E> x = first; |
| for (int i = 0; i < index; i++) |
| x = x.next; |
| return x; |
| } else { |
| Node<E> x = last; |
| for (int i = size - 1; i > index; i--) |
| x = x.prev; |
| return x; |
| } |
| } |
| |
| // Search Operations |
| |
| /** |
| * Returns the index of the first occurrence of the specified element |
| * in this list, or -1 if this list does not contain the element. |
| * More formally, returns the lowest index {@code i} such that |
| * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, |
| * or -1 if there is no such index. |
| * |
| * @param o element to search for |
| * @return the index of the first occurrence of the specified element in |
| * this list, or -1 if this list does not contain the element |
| */ |
| public int indexOf(Object o) { |
| int index = 0; |
| if (o == null) { |
| for (Node<E> x = first; x != null; x = x.next) { |
| if (x.item == null) |
| return index; |
| index++; |
| } |
| } else { |
| for (Node<E> x = first; x != null; x = x.next) { |
| if (o.equals(x.item)) |
| return index; |
| index++; |
| } |
| } |
| return -1; |
| } |
| |
| /** |
| * Returns the index of the last occurrence of the specified element |
| * in this list, or -1 if this list does not contain the element. |
| * More formally, returns the highest index {@code i} such that |
| * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, |
| * or -1 if there is no such index. |
| * |
| * @param o element to search for |
| * @return the index of the last occurrence of the specified element in |
| * this list, or -1 if this list does not contain the element |
| */ |
| public int lastIndexOf(Object o) { |
| int index = size; |
| if (o == null) { |
| for (Node<E> x = last; x != null; x = x.prev) { |
| index--; |
| if (x.item == null) |
| return index; |
| } |
| } else { |
| for (Node<E> x = last; x != null; x = x.prev) { |
| index--; |
| if (o.equals(x.item)) |
| return index; |
| } |
| } |
| return -1; |
| } |
| |
| // Queue operations. |
| |
| /** |
| * Retrieves, but does not remove, the head (first element) of this list. |
| * |
| * @return the head of this list, or {@code null} if this list is empty |
| * @since 1.5 |
| */ |
| public E peek() { |
| final Node<E> f = first; |
| return (f == null) ? null : f.item; |
| } |
| |
| /** |
| * Retrieves, but does not remove, the head (first element) of this list. |
| * |
| * @return the head of this list |
| * @throws NoSuchElementException if this list is empty |
| * @since 1.5 |
| */ |
| public E element() { |
| return getFirst(); |
| } |
| |
| /** |
| * Retrieves and removes the head (first element) of this list. |
| * |
| * @return the head of this list, or {@code null} if this list is empty |
| * @since 1.5 |
| */ |
| public E poll() { |
| final Node<E> f = first; |
| return (f == null) ? null : unlinkFirst(f); |
| } |
| |
| /** |
| * Retrieves and removes the head (first element) of this list. |
| * |
| * @return the head of this list |
| * @throws NoSuchElementException if this list is empty |
| * @since 1.5 |
| */ |
| public E remove() { |
| return removeFirst(); |
| } |
| |
| /** |
| * Adds the specified element as the tail (last element) of this list. |
| * |
| * @param e the element to add |
| * @return {@code true} (as specified by {@link Queue#offer}) |
| * @since 1.5 |
| */ |
| public boolean offer(E e) { |
| return add(e); |
| } |
| |
| // Deque operations |
| /** |
| * Inserts the specified element at the front of this list. |
| * |
| * @param e the element to insert |
| * @return {@code true} (as specified by {@link Deque#offerFirst}) |
| * @since 1.6 |
| */ |
| public boolean offerFirst(E e) { |
| addFirst(e); |
| return true; |
| } |
| |
| /** |
| * Inserts the specified element at the end of this list. |
| * |
| * @param e the element to insert |
| * @return {@code true} (as specified by {@link Deque#offerLast}) |
| * @since 1.6 |
| */ |
| public boolean offerLast(E e) { |
| addLast(e); |
| return true; |
| } |
| |
| /** |
| * Retrieves, but does not remove, the first element of this list, |
| * or returns {@code null} if this list is empty. |
| * |
| * @return the first element of this list, or {@code null} |
| * if this list is empty |
| * @since 1.6 |
| */ |
| public E peekFirst() { |
| final Node<E> f = first; |
| return (f == null) ? null : f.item; |
| } |
| |
| /** |
| * Retrieves, but does not remove, the last element of this list, |
| * or returns {@code null} if this list is empty. |
| * |
| * @return the last element of this list, or {@code null} |
| * if this list is empty |
| * @since 1.6 |
| */ |
| public E peekLast() { |
| final Node<E> l = last; |
| return (l == null) ? null : l.item; |
| } |
| |
| /** |
| * Retrieves and removes the first element of this list, |
| * or returns {@code null} if this list is empty. |
| * |
| * @return the first element of this list, or {@code null} if |
| * this list is empty |
| * @since 1.6 |
| */ |
| public E pollFirst() { |
| final Node<E> f = first; |
| return (f == null) ? null : unlinkFirst(f); |
| } |
| |
| /** |
| * Retrieves and removes the last element of this list, |
| * or returns {@code null} if this list is empty. |
| * |
| * @return the last element of this list, or {@code null} if |
| * this list is empty |
| * @since 1.6 |
| */ |
| public E pollLast() { |
| final Node<E> l = last; |
| return (l == null) ? null : unlinkLast(l); |
| } |
| |
| /** |
| * Pushes an element onto the stack represented by this list. In other |
| * words, inserts the element at the front of this list. |
| * |
| * <p>This method is equivalent to {@link #addFirst}. |
| * |
| * @param e the element to push |
| * @since 1.6 |
| */ |
| public void push(E e) { |
| addFirst(e); |
| } |
| |
| /** |
| * Pops an element from the stack represented by this list. In other |
| * words, removes and returns the first element of this list. |
| * |
| * <p>This method is equivalent to {@link #removeFirst()}. |
| * |
| * @return the element at the front of this list (which is the top |
| * of the stack represented by this list) |
| * @throws NoSuchElementException if this list is empty |
| * @since 1.6 |
| */ |
| public E pop() { |
| return removeFirst(); |
| } |
| |
| /** |
| * Removes the first occurrence of the specified element in this |
| * list (when traversing the list from head to tail). If the list |
| * does not contain the element, it is unchanged. |
| * |
| * @param o element to be removed from this list, if present |
| * @return {@code true} if the list contained the specified element |
| * @since 1.6 |
| */ |
| public boolean removeFirstOccurrence(Object o) { |
| return remove(o); |
| } |
| |
| /** |
| * Removes the last occurrence of the specified element in this |
| * list (when traversing the list from head to tail). If the list |
| * does not contain the element, it is unchanged. |
| * |
| * @param o element to be removed from this list, if present |
| * @return {@code true} if the list contained the specified element |
| * @since 1.6 |
| */ |
| public boolean removeLastOccurrence(Object o) { |
| if (o == null) { |
| for (Node<E> x = last; x != null; x = x.prev) { |
| if (x.item == null) { |
| unlink(x); |
| return true; |
| } |
| } |
| } else { |
| for (Node<E> x = last; x != null; x = x.prev) { |
| if (o.equals(x.item)) { |
| unlink(x); |
| return true; |
| } |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Returns a list-iterator of the elements in this list (in proper |
| * sequence), starting at the specified position in the list. |
| * Obeys the general contract of {@code List.listIterator(int)}.<p> |
| * |
| * The list-iterator is <i>fail-fast</i>: if the list is structurally |
| * modified at any time after the Iterator is created, in any way except |
| * through the list-iterator's own {@code remove} or {@code add} |
| * methods, the list-iterator will throw a |
| * {@code ConcurrentModificationException}. Thus, in the face of |
| * concurrent modification, the iterator fails quickly and cleanly, rather |
| * than risking arbitrary, non-deterministic behavior at an undetermined |
| * time in the future. |
| * |
| * @param index index of the first element to be returned from the |
| * list-iterator (by a call to {@code next}) |
| * @return a ListIterator of the elements in this list (in proper |
| * sequence), starting at the specified position in the list |
| * @throws IndexOutOfBoundsException {@inheritDoc} |
| * @see List#listIterator(int) |
| */ |
| public ListIterator<E> listIterator(int index) { |
| checkPositionIndex(index); |
| return new ListItr(index); |
| } |
| |
| private class ListItr implements ListIterator<E> { |
| private Node<E> lastReturned; |
| private Node<E> next; |
| private int nextIndex; |
| private int expectedModCount = modCount; |
| |
| ListItr(int index) { |
| // assert isPositionIndex(index); |
| next = (index == size) ? null : node(index); |
| nextIndex = index; |
| } |
| |
| public boolean hasNext() { |
| return nextIndex < size; |
| } |
| |
| public E next() { |
| checkForComodification(); |
| if (!hasNext()) |
| throw new NoSuchElementException(); |
| |
| lastReturned = next; |
| next = next.next; |
| nextIndex++; |
| return lastReturned.item; |
| } |
| |
| public boolean hasPrevious() { |
| return nextIndex > 0; |
| } |
| |
| public E previous() { |
| checkForComodification(); |
| if (!hasPrevious()) |
| throw new NoSuchElementException(); |
| |
| lastReturned = next = (next == null) ? last : next.prev; |
| nextIndex--; |
| return lastReturned.item; |
| } |
| |
| public int nextIndex() { |
| return nextIndex; |
| } |
| |
| public int previousIndex() { |
| return nextIndex - 1; |
| } |
| |
| public void remove() { |
| checkForComodification(); |
| if (lastReturned == null) |
| throw new IllegalStateException(); |
| |
| Node<E> lastNext = lastReturned.next; |
| unlink(lastReturned); |
| if (next == lastReturned) |
| next = lastNext; |
| else |
| nextIndex--; |
| lastReturned = null; |
| expectedModCount++; |
| } |
| |
| public void set(E e) { |
| if (lastReturned == null) |
| throw new IllegalStateException(); |
| checkForComodification(); |
| lastReturned.item = e; |
| } |
| |
| public void add(E e) { |
| checkForComodification(); |
| lastReturned = null; |
| if (next == null) |
| linkLast(e); |
| else |
| linkBefore(e, next); |
| nextIndex++; |
| expectedModCount++; |
| } |
| |
| public void forEachRemaining(Consumer<? super E> action) { |
| Objects.requireNonNull(action); |
| while (modCount == expectedModCount && nextIndex < size) { |
| action.accept(next.item); |
| lastReturned = next; |
| next = next.next; |
| nextIndex++; |
| } |
| checkForComodification(); |
| } |
| |
| final void checkForComodification() { |
| if (modCount != expectedModCount) |
| throw new ConcurrentModificationException(); |
| } |
| } |
| |
| private static class Node<E> { |
| E item; |
| Node<E> next; |
| Node<E> prev; |
| |
| Node(Node<E> prev, E element, Node<E> next) { |
| this.item = element; |
| this.next = next; |
| this.prev = prev; |
| } |
| } |
| |
| /** |
| * @since 1.6 |
| */ |
| public Iterator<E> descendingIterator() { |
| return new DescendingIterator(); |
| } |
| |
| /** |
| * Adapter to provide descending iterators via ListItr.previous |
| */ |
| private class DescendingIterator implements Iterator<E> { |
| private final ListItr itr = new ListItr(size()); |
| public boolean hasNext() { |
| return itr.hasPrevious(); |
| } |
| public E next() { |
| return itr.previous(); |
| } |
| public void remove() { |
| itr.remove(); |
| } |
| } |
| |
| @SuppressWarnings("unchecked") |
| private LinkedList<E> superClone() { |
| try { |
| return (LinkedList<E>) super.clone(); |
| } catch (CloneNotSupportedException e) { |
| throw new InternalError(e); |
| } |
| } |
| |
| /** |
| * Returns a shallow copy of this {@code LinkedList}. (The elements |
| * themselves are not cloned.) |
| * |
| * @return a shallow copy of this {@code LinkedList} instance |
| */ |
| public Object clone() { |
| LinkedList<E> clone = superClone(); |
| |
| // Put clone into "virgin" state |
| clone.first = clone.last = null; |
| clone.size = 0; |
| clone.modCount = 0; |
| |
| // Initialize clone with our elements |
| for (Node<E> x = first; x != null; x = x.next) |
| clone.add(x.item); |
| |
| return clone; |
| } |
| |
| /** |
| * Returns an array containing all of the elements in this list |
| * in proper sequence (from first to last element). |
| * |
| * <p>The returned array will be "safe" in that no references to it are |
| * maintained by this list. (In other words, this method must allocate |
| * a new array). The caller is thus free to modify the returned array. |
| * |
| * <p>This method acts as bridge between array-based and collection-based |
| * APIs. |
| * |
| * @return an array containing all of the elements in this list |
| * in proper sequence |
| */ |
| public Object[] toArray() { |
| Object[] result = new Object[size]; |
| int i = 0; |
| for (Node<E> x = first; x != null; x = x.next) |
| result[i++] = x.item; |
| return result; |
| } |
| |
| /** |
| * Returns an array containing all of the elements in this list in |
| * proper sequence (from first to last element); the runtime type of |
| * the returned array is that of the specified array. If the list fits |
| * in the specified array, it is returned therein. Otherwise, a new |
| * array is allocated with the runtime type of the specified array and |
| * the size of this list. |
| * |
| * <p>If the list fits in the specified array with room to spare (i.e., |
| * the array has more elements than the list), the element in the array |
| * immediately following the end of the list is set to {@code null}. |
| * (This is useful in determining the length of the list <i>only</i> if |
| * the caller knows that the list does not contain any null elements.) |
| * |
| * <p>Like the {@link #toArray()} method, this method acts as bridge between |
| * array-based and collection-based APIs. Further, this method allows |
| * precise control over the runtime type of the output array, and may, |
| * under certain circumstances, be used to save allocation costs. |
| * |
| * <p>Suppose {@code x} is a list known to contain only strings. |
| * The following code can be used to dump the list into a newly |
| * allocated array of {@code String}: |
| * |
| * <pre> |
| * String[] y = x.toArray(new String[0]);</pre> |
| * |
| * Note that {@code toArray(new Object[0])} is identical in function to |
| * {@code toArray()}. |
| * |
| * @param a the array into which the elements of the list are to |
| * be stored, if it is big enough; otherwise, a new array of the |
| * same runtime type is allocated for this purpose. |
| * @return an array containing the elements of the list |
| * @throws ArrayStoreException if the runtime type of the specified array |
| * is not a supertype of the runtime type of every element in |
| * this list |
| * @throws NullPointerException if the specified array is null |
| */ |
| @SuppressWarnings("unchecked") |
| public <T> T[] toArray(T[] a) { |
| if (a.length < size) |
| a = (T[])java.lang.reflect.Array.newInstance( |
| a.getClass().getComponentType(), size); |
| int i = 0; |
| Object[] result = a; |
| for (Node<E> x = first; x != null; x = x.next) |
| result[i++] = x.item; |
| |
| if (a.length > size) |
| a[size] = null; |
| |
| return a; |
| } |
| |
| private static final long serialVersionUID = 876323262645176354L; |
| |
| /** |
| * Saves the state of this {@code LinkedList} instance to a stream |
| * (that is, serializes it). |
| * |
| * @serialData The size of the list (the number of elements it |
| * contains) is emitted (int), followed by all of its |
| * elements (each an Object) in the proper order. |
| */ |
| private void writeObject(java.io.ObjectOutputStream s) |
| throws java.io.IOException { |
| // Write out any hidden serialization magic |
| s.defaultWriteObject(); |
| |
| // Write out size |
| s.writeInt(size); |
| |
| // Write out all elements in the proper order. |
| for (Node<E> x = first; x != null; x = x.next) |
| s.writeObject(x.item); |
| } |
| |
| /** |
| * Reconstitutes this {@code LinkedList} instance from a stream |
| * (that is, deserializes it). |
| */ |
| @SuppressWarnings("unchecked") |
| private void readObject(java.io.ObjectInputStream s) |
| throws java.io.IOException, ClassNotFoundException { |
| // Read in any hidden serialization magic |
| s.defaultReadObject(); |
| |
| // Read in size |
| int size = s.readInt(); |
| |
| // Read in all elements in the proper order. |
| for (int i = 0; i < size; i++) |
| linkLast((E)s.readObject()); |
| } |
| |
| /** |
| * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em> |
| * and <em>fail-fast</em> {@link Spliterator} over the elements in this |
| * list. |
| * |
| * <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and |
| * {@link Spliterator#ORDERED}. Overriding implementations should document |
| * the reporting of additional characteristic values. |
| * |
| * @implNote |
| * The {@code Spliterator} additionally reports {@link Spliterator#SUBSIZED} |
| * and implements {@code trySplit} to permit limited parallelism.. |
| * |
| * @return a {@code Spliterator} over the elements in this list |
| * @since 1.8 |
| */ |
| @Override |
| public Spliterator<E> spliterator() { |
| return new LLSpliterator<E>(this, -1, 0); |
| } |
| |
| /** A customized variant of Spliterators.IteratorSpliterator */ |
| static final class LLSpliterator<E> implements Spliterator<E> { |
| static final int BATCH_UNIT = 1 << 10; // batch array size increment |
| static final int MAX_BATCH = 1 << 25; // max batch array size; |
| final LinkedList<E> list; // null OK unless traversed |
| Node<E> current; // current node; null until initialized |
| int est; // size estimate; -1 until first needed |
| int expectedModCount; // initialized when est set |
| int batch; // batch size for splits |
| |
| LLSpliterator(LinkedList<E> list, int est, int expectedModCount) { |
| this.list = list; |
| this.est = est; |
| this.expectedModCount = expectedModCount; |
| } |
| |
| final int getEst() { |
| int s; // force initialization |
| final LinkedList<E> lst; |
| if ((s = est) < 0) { |
| if ((lst = list) == null) |
| s = est = 0; |
| else { |
| expectedModCount = lst.modCount; |
| current = lst.first; |
| s = est = lst.size; |
| } |
| } |
| return s; |
| } |
| |
| public long estimateSize() { return (long) getEst(); } |
| |
| public Spliterator<E> trySplit() { |
| Node<E> p; |
| int s = getEst(); |
| if (s > 1 && (p = current) != null) { |
| int n = batch + BATCH_UNIT; |
| if (n > s) |
| n = s; |
| if (n > MAX_BATCH) |
| n = MAX_BATCH; |
| Object[] a = new Object[n]; |
| int j = 0; |
| do { a[j++] = p.item; } while ((p = p.next) != null && j < n); |
| current = p; |
| batch = j; |
| est = s - j; |
| return Spliterators.spliterator(a, 0, j, Spliterator.ORDERED); |
| } |
| return null; |
| } |
| |
| public void forEachRemaining(Consumer<? super E> action) { |
| Node<E> p; int n; |
| if (action == null) throw new NullPointerException(); |
| if ((n = getEst()) > 0 && (p = current) != null) { |
| current = null; |
| est = 0; |
| do { |
| E e = p.item; |
| p = p.next; |
| action.accept(e); |
| } while (p != null && --n > 0); |
| } |
| if (list.modCount != expectedModCount) |
| throw new ConcurrentModificationException(); |
| } |
| |
| public boolean tryAdvance(Consumer<? super E> action) { |
| Node<E> p; |
| if (action == null) throw new NullPointerException(); |
| if (getEst() > 0 && (p = current) != null) { |
| --est; |
| E e = p.item; |
| current = p.next; |
| action.accept(e); |
| if (list.modCount != expectedModCount) |
| throw new ConcurrentModificationException(); |
| return true; |
| } |
| return false; |
| } |
| |
| public int characteristics() { |
| return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED; |
| } |
| } |
| |
| } |
