Java學習之LinkedList
阿新 • • 發佈:2019-02-04
我們都站在巨人的肩膀上
1.LinkedList 原始碼:
public class LinkedList<E>
extends AbstractSequentialList<E>
implements List<E>, Deque<E>, Cloneable, java.io.Serializable
{
// transient修飾的欄位將不進行序列化,該變數內容在序列化後無法獲得訪問
transient int size = 0;
transient Node<E> first;
transient Node<E> last;
public LinkedList() {
}
// 指定集合建立LinkedList
public LinkedList(Collection<? extends E> c) {
this();
addAll(c);
}
// 設定頭節點
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++;
}
// 設定尾節點
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++;
}
// 在非空節點前插入元素
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++;
}
//首元素設定為null,GC回收
private E unlinkFirst(Node<E> f) {
// assert f == first && f != null;
final E element = f.item;
final Node<E> next = f.next;
// item、next 同時為null,GC才能回收
f.item = null;
f.next = null; // help GC
first = next;
if (next == null)
last = null;
else
next.prev = null;
size--;
modCount++;
return element;
}
//末位設定為null,GC回收
private E unlinkLast(Node<E> l) {
// assert l == last && l != null;
final E element = l.item;
final Node<E> prev = l.prev;
// item、next 同時為null,GC才能回收
l.item = null;
l.prev = null; // help GC
last = prev;
if (prev == null)
first = null;
else
prev.next = null;
size--;
modCount++;
return element;
}
// 指定元素設定為null
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;
}
// 獲取頭結點
public E getFirst() {
final Node<E> f = first;
if (f == null)
throw new NoSuchElementException();
return f.item;
}
// 獲取尾節點
public E getLast() {
final Node<E> l = last;
if (l == null)
throw new NoSuchElementException();
return l.item;
}
// 刪除首節點
public E removeFirst() {
final Node<E> f = first;
if (f == null)
throw new NoSuchElementException();
return unlinkFirst(f);
}
// 刪除尾節點
public E removeLast() {
final Node<E> l = last;
if (l == null)
throw new NoSuchElementException();
return unlinkLast(l);
}
// 新增首節點、實際上呼叫的是linkFirst,對linkFirst進行封裝
public void addFirst(E e) {
linkFirst(e);
}
// 新增尾節點、實際上呼叫的是linkLast,對linkLast進行封裝
public void addLast(E e) {
linkLast(e);
}
// 是否包含此元素
public boolean contains(Object o) {
return indexOf(o) != -1;
}
public int size() {
return size;
}
// 預設在尾節點新增元素,成功返回true
public boolean add(E e) {
linkLast(e);
return true;
}
// 刪除節點
public boolean remove(Object o) {
if (o == null) {
// 遍歷樹
for (Node<E> x = first; x != null; x = x.next) {
if (x.item == null) {
// 將該元素設定為null,GC回收
unlink(x);
return true;
}
}
} else {
for (Node<E> x = first; x != null; x = x.next) {
if (o.equals(x.item)) {
// 將該元素設定為null,GC回收
unlink(x);
return true;
}
}
}
return false;
}
// 新增尾節點處新增集合
public boolean addAll(Collection<? extends E> c) {
return addAll(size, c);
}
// 指定位置新增集合
public boolean addAll(int index, Collection<? extends E> c) {
// 檢查下標
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;
}
// 清空
public void clear() {
// 整個集合設定為null
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++;
}
// 根據下標獲取元素
public E get(int index) {
// 檢查下標
checkElementIndex(index);
return node(index).item;
}
// 根據下標設定元素
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));
}
public E remove(int index) {
checkElementIndex(index);
return unlink(node(index));
}
private boolean isElementIndex(int index) {
return index >= 0 && index < size;
}
private boolean isPositionIndex(int index) {
return index >= 0 && index <= size;
}
// 越界資訊
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));
}
// 返回節點資訊
Node<E> node(int index) {
// assert isElementIndex(index);
// 獲取節點,size >>1 更高效
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;
}
}
// 檢查該元素釋放存在,存在返回下標,不存在返回-1
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;
}
// 從後往前遍歷獲取元素,返回下標
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;
}
public E peek() {
final Node<E> f = first;
return (f == null) ? null : f.item;
}
public E element() {
return getFirst();
}
public E poll() {
final Node<E> f = first;
return (f == null) ? null : unlinkFirst(f);
}
public E remove() {
return removeFirst();
}
public boolean offer(E e) {
return add(e);
}
public boolean offerFirst(E e) {
addFirst(e);
return true;
}
public boolean offerLast(E e) {
addLast(e);
return true;
}
public E peekFirst() {
final Node<E> f = first;
return (f == null) ? null : f.item;
}
public E peekLast() {
final Node<E> l = last;
return (l == null) ? null : l.item;
}
public E pollFirst() {
final Node<E> f = first;
return (f == null) ? null : unlinkFirst(f);
}
public E pollLast() {
final Node<E> l = last;
return (l == null) ? null : unlinkLast(l);
}
public void push(E e) {
addFirst(e);
}
public E pop() {
return removeFirst();
}
public boolean removeFirstOccurrence(Object o) {
return remove(o);
}
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;
}
// 迭代器
public ListIterator<E> listIterator(int index) {
checkPositionIndex(index);
return new ListItr(index);
}
// 重寫 迭代器
private class ListItr implements ListIterator<E> {
private Node<E> lastReturned = null;
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;
// 迭代器執行次數
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++;
}
// 檢查linkedList操作次數與迭代器操作次數釋放相同
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();
}
// 返回一個迭代器在此雙端佇列以逆向順序的元素
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();
}
}
// 克隆後返回LinkedList集合
@SuppressWarnings("unchecked")
private LinkedList<E> superClone() {
try {
return (LinkedList<E>) super.clone();
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
}
// 克隆
public Object clone() {
LinkedList<E> clone = superClone();
// 克隆放為初始狀態
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;
}
//物件轉為LinkedList
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;
}
// 指定集合轉為LinkedList
@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;
}
// 序列化
private static final long serialVersionUID = 876323262645176354L;
// 寫入流
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
//寫入所有資訊和隱藏資訊
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);
}
// 讀出流
@SuppressWarnings("unchecked")
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// 讀所有資訊和隱藏資訊
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());
}
}