Java之LinkedList源码解读（JDK 1.8）

java.util.LinkedList

双向链表实现的List。
基于JDK 1.8。
没有使用标准的注释，并适当调整了代码的缩进以方便介绍。
里面很多方法的实现是一样的，不过可以让外界感觉其提供了更多的行为。
需要花比ArrayList更多一点的时间理解

package com.anxpp.thinkinjava.chapter11.sourse;
import java.util.AbstractSequentialList;
import java.util.Collection;
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.Spliterator;
import java.util.Spliterators;
import java.util.function.Consumer;
/**
* LinkedList底层使用双向链表，实现了List和deque。实现所有的可选List操作，并可以只有所有元素（包括空值）
* 其大小理论上仅受内存大小的限制
*
* 所有的操作都可以作为一个双联列表来执行（及对双向链表操作）。
* 把对链表的操作封装起来，并对外提供看起来是对普通列表操作的方法。
* 遍历从起点、终点、或指定位置开始
* 内部方法，注释会描述为节点的操作(如删除第一个节点)，公开的方法会描述为元素的操作(如删除第一个元素)
*
* LinkedList不是线程安全的，如果在多线程中使用（修改），需要在外部作同步处理。
*
* 需要弄清元素（节点）的索引和位置的区别，不然有几个地方不好理解，具体在碰到的地方会解释。
*
* 迭代器可以快速报错
*/
public class LinkedList<E> extends AbstractSequentialList<E> implements List<E>, Deque<E>, Cloneable, java.io.Serializable
{
//容量
transient int size = 0;
//首节点
transient Node<E> first;
//尾节点
transient Node<E> last;
//默认构造函数
public LinkedList() {
}
//通过一个集合初始化LinkedList，元素顺序有这个集合的迭代器返回顺序决定
public LinkedList(Collection<? extends E> c) {
this();
addAll(c);
}
//使用对应参数作为第一个节点，内部使用
private void linkFirst(E e) {
final Node<E> f = first;//得到首节点
final Node<E> newNode = new Node<>(null, e, f);//创建一个节点
first = newNode;        //设置首节点
if (f == null)
last = newNode;     //如果之前首节点为空(size==0)，那么尾节点就是首节点
else
f.prev = newNode;   //如果之前首节点不为空，之前的首节点的前一个节点为当前首节点
size++;                 //长度+1
modCount++;             //修改次数+1
}
//使用对应参数作为尾节点
void linkLast(E e) {
final Node<E> l = last; //得到尾节点
final Node<E> newNode = new Node<>(l, e, null);//使用参数创建一个节点
last = newNode;         //设置尾节点
if (l == null)
first = newNode;    //如果之前尾节点为空(size==0)，首节点即尾节点
else
l.next = newNode;   //如果之前尾节点不为空，之前的尾节点的后一个就是当前的尾节点
size++;
modCount++;
}
//在指定节点前插入节点，节点succ不能为空
void linkBefore(E e, Node<E> succ) {
final Node<E> pred = succ.prev;//获取前一个节点
final Node<E> newNode = new Node<>(pred, e, succ);//使用参数创建新的节点，向前指向前一个节点，向后指向当前节点
succ.prev = newNode;//当前节点指向新的节点
if (pred == null)
first = newNode;//如果前一个节点为null，新的节点就是首节点
else
pred.next = newNode;//如果存在前节点，那么前节点的向后指向新节点
size++;
modCount++;
}
//删除首节点并返回删除前首节点的值，内部使用
private E unlinkFirst(Node<E> f) {
final E element = f.item;//获取首节点的值
final Node<E> next = f.next;//得到下一个节点
f.item = null;
f.next = null;      //便于垃圾回收期清理
first = next;       //首节点的下一个节点成为新的首节点
if (next == null)
last = null;    //如果不存在下一个节点，则首尾都为null(空表)
else
next.prev = null;//如果存在下一个节点，那它向前指向null
size--;
modCount++;
return element;
}
//删除尾节点并返回删除前尾节点的值，内部使用
private E unlinkLast(Node<E> l) {
final E element = l.item;//获取值
final Node<E> prev = l.prev;//获取尾节点前一个节点
l.item = null;
l.prev = null;      //便于垃圾回收期清理
last = prev;        //前一个节点成为新的尾节点
if (prev == null)
first = null;   //如果前一个节点不存在，则首尾都为null(空表)
else
prev.next = null;//如果前一个节点存在，先后指向null
size--;
modCount++;
return element;
}
//删除指定节点并返回被删除的元素值
E unlink(Node<E> x) {
//获取当前值和前后节点
final E element = x.item;
final Node<E> next = x.next;
final Node<E> prev = x.prev;
if (prev == null) {
first = next;   //如果前一个节点为空(如当前节点为首节点)，后一个节点成为新的首节点
} else {
prev.next = next;//如果前一个节点不为空，那么他先后指向当前的下一个节点
x.prev = null;  //方便gc回收
}
if (next == null) {
last = prev;    //如果后一个节点为空(如当前节点为尾节点)，当前节点前一个成为新的尾节点
} else {
next.prev = prev;//如果后一个节点不为空，后一个节点向前指向当前的前一个节点
x.next = null;  //方便gc回收
}
x.item = null;      //方便gc回收
size--;
modCount++;
return element;
}
//获取第一个元素
public E getFirst() {
final Node<E> f = first;//得到首节点
if (f == null)          //如果为空，抛出异常
throw new NoSuchElementException();
return f.item;
}
//获取最后一个元素
public E getLast() {
final Node<E> l = last;//得到尾节点
if (l == null)          //如果为空，抛出异常
throw new NoSuchElementException();
return l.item;
}
//删除第一个元素并返回删除的元素
public E removeFirst() {
final Node<E> f = first;//得到第一个节点
if (f == null)          //如果为空，抛出异常
throw new NoSuchElementException();
return unlinkFirst(f);
}
//删除最后一个元素并返回删除的值
public E removeLast() {
final Node<E> l = last;//得到最后一个节点
if (l == null)          //如果为空，抛出异常
throw new NoSuchElementException();
return unlinkLast(l);
}
//添加元素作为第一个元素
public void addFirst(E e) {
linkFirst(e);
}
//店家元素作为最后一个元素
public void addLast(E e) {
linkLast(e);
}
//检查是否包含某个元素，返回bool
public boolean contains(Object o) {
return indexOf(o) != -1;//返回指定元素的索引位置，不存在就返回-1，然后比较返回bool值
}
//返回列表长度
public int size() {
return size;
}
//添加一个元素，默认添加到末尾作为最后一个元素
public boolean add(E e) {
linkLast(e);
return true;
}
//删除指定元素，默认从first节点开始，删除第一次出现的那个元素
public boolean remove(Object o) {
//会根据是否为null分开处理。若值不是null，会用到对象的equals()方法
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;
}
//添加指定集合的元素到列表，默认从最后开始添加
public boolean addAll(Collection<? extends E> c) {
return addAll(size, c);//size表示最后一个位置，可以理解为元素的位置分别为1~size
}
//从指定位置（而不是下标！下标即索引从0开始，位置可以看做从1开始，其实也是0）后面添加指定集合的元素到列表中，只要有至少一次添加就会返回true
//index换成position应该会更好理解，所以也就是从索引为index(position)的元素的前面索引为index-1的后面添加！
//当然位置可以为0啊，为0的时候就是从位置0(虽然它不存在)后面开始添加嘛，所以理所当前就是添加到第一个位置（位置1的前面）的前面了啊！
//比如列表：0 1 2 3，如果此处index=4(实际索引为3)，就是在元素3后面添加；如果index=3(实际索引为2)，就在元素2后面添加。
//原谅我的表达水平，我已经尽力解释了...
public boolean addAll(int index, Collection<? extends E> c) {
checkPositionIndex(index);  //检查索引是否正确（0<=index<=size）
Object[] a = c.toArray();   //得到元素数组
int numNew = a.length;      //得到元素个数
if (numNew == 0)            //若没有元素要添加，直接返回false
return false;
Node<E> pred, succ;
if (index == size) {    //如果是在末尾开始添加，当前节点后一个节点初始化为null，前一个节点为尾节点
succ = null;        //这里可以看做node(index)，不过index=size了（index最大只能是size-1），所以这里的succ只能=null，也方便后面判断
pred = last;        //这里看做noede(index-1)，当然实现是不能这么写的，看做这样只是为了好理解，所以就是在node(index-1的后面开始添加元素)
} else {                //如果不是从末尾开始添加，当前位置的节点为指定位置的节点，前一个节点为要添加的节点的前一个节点
succ = node(index); //添加好元素后(整个新加的)的后一个节点
pred = succ.prev;   //这里依然是node(index-1)
}
//遍历数组并添加到列表中
for (Object o : a) {
@SuppressWarnings("unchecked")
E e = (E) o;
Node<E> newNode = new Node<>(pred, e, null);//创建一个节点，向前指向上面得到的前节点
if (pred == null)
first = newNode;    //若果前节点为null，则新加的节点为首节点
else
pred.next = newNode;//如果存在前节点，前节点会向后指向新加的节点
pred = newNode;         //新加的节点成为前一个节点
}
if (succ == null) {
//pred.next = null  //加上这句也可以更好的理解
last = pred;        //如果是从最后开始添加的，则最后添加的节点成为尾节点
} else {
pred.next = succ;   //如果不是从最后开始添加的，则最后添加的节点向后指向之前得到的后续第一个节点
succ.prev = pred;   //当前，后续的第一个节点也应改为向前指向最后一个添加的节点
}
size += numNew;
modCount++;
return true;
}
//清空表
public void clear() {
//方便gc回收垃圾
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++;
}
//获取指定索引的节点的值
public E get(int index) {
checkElementIndex(index);
return node(index).item;
}
//修改指定索引的值并返回之前的值
public E set(int index, E element) {
checkElementIndex(index);
Node<E> x = node(index);
E oldVal = x.item;
x.item = element;
return oldVal;
}
//指定位置后面（即索引为这个值的元素的前面）添加元素
public void add(int index, E element) {
checkPositionIndex(index);
if (index == size)
linkLast(element);  //如果指定位置为最后，则添加到链表最后
else                    //如果指定位置不是最后，则添加到指定位置前
linkBefore(element, node(index));
}
//删除指定位置的元素，
public E remove(int index) {
checkElementIndex(index);
return unlink(node(index));
}
//检查索引是否超出范围，因为元素索引是0~size-1的，所以index必须满足0<=index<size
private boolean isElementIndex(int index) {
return index >= 0 && index < size;
}
//检查位置是否超出范围，index必须在index~size之间（含），如果超出，返回false
private boolean isPositionIndex(int index) {
return index >= 0 && index <= size;
}
//异常详情
private String outOfBoundsMsg(int index) {
return "Index: "+index+", Size: "+size;
}
//检查元素索引是否超出范围，若已超出，就抛出异常
private void checkElementIndex(int index) {
if (!isElementIndex(index))
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
//检查位置是否超出范围，若已超出，就抛出异常
private void checkPositionIndex(int index) {
if (!isPositionIndex(index))
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
//获取指定位置的节点
Node<E> node(int index) {
//如果位置索引小于列表长度的一半(或一半减一)，从前面开始遍历；否则，从后面开始遍历
if (index < (size >> 1)) {
Node<E> x = first;//index==0时不会循环，直接返回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;
}
}
//获取指定元素从first开始的索引位置，不存在就返回-1
//不能按条件双向找了，所以通常根据索引获得元素的速度比通过元素获得索引的速度快
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;
}
//获取指定元素从first开始最后出现的索引，不存在就返回-1
//但实际查找是从last开始的
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;
}
//提供普通队列和双向队列的功能，当然，也可以实现栈，FIFO，FILO
//出队（从前端），获得第一个元素，不存在会返回null，不会删除元素（节点）
public E peek() {
final Node<E> f = first;
return (f == null) ? null : f.item;
}
//出队（从前端），不删除元素，若为null会抛出异常而不是返回null
public E element() {
return getFirst();
}
//出队（从前端），如果不存在会返回null，存在的话会返回值并移除这个元素（节点）
public E poll() {
final Node<E> f = first;
return (f == null) ? null : unlinkFirst(f);
}
//出队（从前端），如果不存在会抛出异常而不是返回null，存在的话会返回值并移除这个元素（节点）
public E remove() {
return removeFirst();
}
//入队（从后端），始终返回true
public boolean offer(E e) {
return add(e);
}
//入队（从前端），始终返回true
public boolean offerFirst(E e) {
addFirst(e);
return true;
}
//入队（从后端），始终返回true
public boolean offerLast(E e) {
addLast(e);//linkLast(e)
return true;
}
//出队（从前端），获得第一个元素，不存在会返回null，不会删除元素（节点）
public E peekFirst() {
final Node<E> f = first;
return (f == null) ? null : f.item;
}
//出队（从后端），获得最后一个元素，不存在会返回null，不会删除元素（节点）
public E peekLast() {
final Node<E> l = last;
return (l == null) ? null : l.item;
}
//出队（从前端），获得第一个元素，不存在会返回null，会删除元素（节点）
public E pollFirst() {
final Node<E> f = first;
return (f == null) ? null : unlinkFirst(f);
}
//出队（从后端），获得最后一个元素，不存在会返回null，会删除元素（节点）
public E pollLast() {
final Node<E> l = last;
return (l == null) ? null : unlinkLast(l);
}
//入栈，从前面添加
public void push(E e) {
addFirst(e);
}
//出栈，返回栈顶元素，从前面移除（会删除）
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();
}
}
//节点的数据结构，包含前后节点的引用和当前节点
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;
}
}
//返回迭代器
public Iterator<E> descendingIterator() {
return new DescendingIterator();
}
//因为采用链表实现，所以迭代器很简单
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
;
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;
}
}
}