xdean.jex.extra.collection.LinkedList Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*/
package xdean.jex.extra.collection;
import java.util.AbstractSequentialList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.ConcurrentModificationException;
import java.util.Deque;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.Queue;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.Consumer;
import xdean.codecov.CodecovIgnore;
/**
* Copy from system library, jdk 1.8.0_112u
*
*
*
* Doubly-linked list implementation of the {@code List} and {@code Deque} interfaces. Implements all optional list
* operations, and permits all elements (including {@code null}).
*
*
* 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.
*
*
* Note that this implementation is not synchronized. If multiple threads access a linked list
* concurrently, and at least one of the threads modifies the list structurally, it must 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:
*
*
* List list = Collections.synchronizedList(new LinkedList(...));
*
*
*
* The iterators returned by this class's {@code iterator} and {@code listIterator} methods are fail-fast: 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.
*
*
* 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: the fail-fast behavior of iterators should be used only to detect
* bugs.
*
*
* This class is a member of the Java Collections
* Framework.
*
* @author Josh Bloch
* @see List
* @see ArrayList
* @since 1.2
* @param the type of elements held in this collection
*/
@CodecovIgnore
class LinkedList
extends AbstractSequentialList
implements List, Deque, 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 first;
/**
* Pointer to last node. Invariant: (first == null && last == null) || (last.next == null && last.item != null)
*/
transient Node 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 c) {
this();
addAll(c);
}
/**
* Links e as first element.
*/
private void linkFirst(E e) {
final Node f = first;
final Node 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 l = last;
final Node 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 succ) {
// assert succ != null;
final Node pred = succ.prev;
final Node 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 f) {
// assert f == first && f != null;
final E element = f.item;
final Node 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 l) {
// assert l == last && l != null;
final E element = l.item;
final Node 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 x) {
// assert x != null;
final E element = x.item;
final Node next = x.next;
final Node 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
*/
@Override
public E getFirst() {
final Node 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
*/
@Override
public E getLast() {
final Node 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
*/
@Override
public E removeFirst() {
final Node 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
*/
@Override
public E removeLast() {
final Node 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
*/
@Override
public void addFirst(E e) {
linkFirst(e);
}
/**
* Appends the specified element to the end of this list.
*
*
* This method is equivalent to {@link #add}.
*
* @param e the element to add
*/
@Override
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
* (o==null ? e==null : o.equals(e)).
*
* @param o element whose presence in this list is to be tested
* @return {@code true} if this list contains the specified element
*/
@Override
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
*/
@Override
public int size() {
return size;
}
/**
* Appends the specified element to the end of this list.
*
*
* 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})
*/
@Override
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
* (o==null ? get(i)==null : o.equals(get(i))) (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
*/
@Override
public boolean remove(Object o) {
if (o == null) {
for (Node x = first; x != null; x = x.next) {
if (x.item == null) {
unlink(x);
return true;
}
}
} else {
for (Node 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
*/
@Override
public boolean addAll(Collection 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
*/
@Override
public boolean addAll(int index, Collection c) {
checkPositionIndex(index);
Object[] a = c.toArray();
int numNew = a.length;
if (numNew == 0) {
return false;
}
Node 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 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.
*/
@Override
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 x = first; x != null;) {
Node 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}
*/
@Override
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}
*/
@Override
public E set(int index, E element) {
checkElementIndex(index);
Node 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}
*/
@Override
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}
*/
@Override
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 node(int index) {
// assert isElementIndex(index);
if (index < (size >> 1)) {
Node x = first;
for (int i = 0; i < index; i++) {
x = x.next;
}
return x;
} else {
Node 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
* (o==null ? get(i)==null : o.equals(get(i))), 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
*/
@Override
public int indexOf(Object o) {
int index = 0;
if (o == null) {
for (Node x = first; x != null; x = x.next) {
if (x.item == null) {
return index;
}
index++;
}
} else {
for (Node 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
* (o==null ? get(i)==null : o.equals(get(i))), 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
*/
@Override
public int lastIndexOf(Object o) {
int index = size;
if (o == null) {
for (Node x = last; x != null; x = x.prev) {
index--;
if (x.item == null) {
return index;
}
}
} else {
for (Node 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
*/
@Override
public E peek() {
final Node 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
*/
@Override
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
*/
@Override
public E poll() {
final Node 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
*/
@Override
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
*/
@Override
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
*/
@Override
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
*/
@Override
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
*/
@Override
public E peekFirst() {
final Node 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
*/
@Override
public E peekLast() {
final Node 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
*/
@Override
public E pollFirst() {
final Node 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
*/
@Override
public E pollLast() {
final Node 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.
*
*
* This method is equivalent to {@link #addFirst}.
*
* @param e the element to push
* @since 1.6
*/
@Override
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.
*
*
* 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
*/
@Override
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
*/
@Override
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
*/
@Override
public boolean removeLastOccurrence(Object o) {
if (o == null) {
for (Node x = last; x != null; x = x.prev) {
if (x.item == null) {
unlink(x);
return true;
}
}
} else {
for (Node 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)}.
*
*
* The list-iterator is fail-fast: 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)
*/
@Override
public ListIterator listIterator(int index) {
checkPositionIndex(index);
return new ListItr(index);
}
private class ListItr implements ListIterator {
private Node lastReturned;
private Node next;
private int nextIndex;
private int expectedModCount = modCount;
ListItr(int index) {
// assert isPositionIndex(index);
next = (index == size) ? null : node(index);
nextIndex = index;
}
@Override
public boolean hasNext() {
return nextIndex < size;
}
@Override
public E next() {
checkForComodification();
if (!hasNext()) {
throw new NoSuchElementException();
}
lastReturned = next;
next = next.next;
nextIndex++;
return lastReturned.item;
}
@Override
public boolean hasPrevious() {
return nextIndex > 0;
}
@Override
public E previous() {
checkForComodification();
if (!hasPrevious()) {
throw new NoSuchElementException();
}
lastReturned = next = (next == null) ? last : next.prev;
nextIndex--;
return lastReturned.item;
}
@Override
public int nextIndex() {
return nextIndex;
}
@Override
public int previousIndex() {
return nextIndex - 1;
}
@Override
public void remove() {
checkForComodification();
if (lastReturned == null) {
throw new IllegalStateException();
}
Node lastNext = lastReturned.next;
unlink(lastReturned);
if (next == lastReturned) {
next = lastNext;
} else {
nextIndex--;
}
lastReturned = null;
expectedModCount++;
}
@Override
public void set(E e) {
if (lastReturned == null) {
throw new IllegalStateException();
}
checkForComodification();
lastReturned.item = e;
}
@Override
public void add(E e) {
checkForComodification();
lastReturned = null;
if (next == null) {
linkLast(e);
} else {
linkBefore(e, next);
}
nextIndex++;
expectedModCount++;
}
@Override
public void forEachRemaining(Consumer 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();
}
}
}
static class Node {
E item;
Node next;
Node prev;
Node(Node prev, E element, Node next) {
this.item = element;
this.next = next;
this.prev = prev;
}
}
/**
* @since 1.6
*/
@Override
public Iterator descendingIterator() {
return new DescendingIterator();
}
/**
* Adapter to provide descending iterators via ListItr.previous
*/
private class DescendingIterator implements Iterator {
private final ListItr itr = new ListItr(size());
@Override
public boolean hasNext() {
return itr.hasPrevious();
}
@Override
public E next() {
return itr.previous();
}
@Override
public void remove() {
itr.remove();
}
}
@SuppressWarnings("unchecked")
private LinkedList superClone() {
try {
return (LinkedList) 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
*/
@Override
public Object clone() {
LinkedList 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 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).
*
*
* 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.
*
*
* 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
*/
@Override
public Object[] toArray() {
Object[] result = new Object[size];
int i = 0;
for (Node 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.
*
*
* 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 only if the caller knows that the list does not contain any null
* elements.)
*
*
* 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.
*
*
* 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}:
*
*
* String[] y = x.toArray(new String[0]);
*
*
* 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
*/
@Override
@SuppressWarnings("unchecked")
public 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 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 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 late-binding and fail-fast {@link Spliterator}
* over the elements in this list.
*
*
* 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 spliterator() {
return new LLSpliterator(this, -1, 0);
}
/** A customized variant of Spliterators.IteratorSpliterator */
static final class LLSpliterator implements Spliterator {
static final int BATCH_UNIT = 1 << 10; // batch array size increment
static final int MAX_BATCH = 1 << 25; // max batch array size;
final LinkedList list; // null OK unless traversed
Node 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 list, int est, int expectedModCount) {
this.list = list;
this.est = est;
this.expectedModCount = expectedModCount;
}
final int getEst() {
int s; // force initialization
final LinkedList 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;
}
@Override
public long estimateSize() {
return getEst();
}
@Override
public Spliterator trySplit() {
Node 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;
}
@Override
public void forEachRemaining(Consumer action) {
Node 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();
}
}
@Override
public boolean tryAdvance(Consumer action) {
Node 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;
}
@Override
public int characteristics() {
return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
}
}
}