Java LinkedList

LinkedList是基于双向链表实现的，先看构造方法和方法

• Constructor Summary

  Constructors

  Constructor	Description
  LinkedList()	Constructs an empty list.
  LinkedList​(Collection<? extends E> c)	Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.

• Method Summary

  All MethodsInstance MethodsConcrete Methods

  Modifier and Type	Method	Description
  void	add​(int index,E element)	Inserts the specified element at the specified position in this list.
  boolean	add​(E e)	Appends the specified element to the end of this list.
  boolean	addAll​(int index,Collection<? extendsE> c)	Inserts all of the elements in the specified collection into this list, starting at the specified position.
  boolean	addAll​(Collection<? extends E> c)	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.
  void	addFirst​(E e)	Inserts the specified element at the beginning of this list.
  void	addLast​(E e)	Appends the specified element to the end of this list.
  void	clear()	Removes all of the elements from this list.
  Object	clone()	Returns a shallow copy of this LinkedList.
  boolean	contains​(Object o)	Returns true if this list contains the specified element.
  Iterator<E>	descendingIterator()	Returns an iterator over the elements in this deque in reverse sequential order.
  E	element()	Retrieves, but does not remove, the head (first element) of this list.
  E	get​(int index)	Returns the element at the specified position in this list.
  E	getFirst()	Returns the first element in this list.
  E	getLast()	Returns the last element in this list.
  int	indexOf​(Object o)	Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
  int	lastIndexOf​(Object o)	Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
  ListIterator<E>	listIterator​(int index)	Returns a list-iterator of the elements in this list (in proper sequence), starting at the specified position in the list.
  boolean	offer​(E e)	Adds the specified element as the tail (last element) of this list.
  boolean	offerFirst​(E e)	Inserts the specified element at the front of this list.
  boolean	offerLast​(E e)	Inserts the specified element at the end of this list.
  E	peek()	Retrieves, but does not remove, the head (first element) of this list.
  E	peekFirst()	Retrieves, but does not remove, the first element of this list, or returns null if this list is empty.
  E	peekLast()	Retrieves, but does not remove, the last element of this list, or returns null if this list is empty.
  E	poll()	Retrieves and removes the head (first element) of this list.
  E	pollFirst()	Retrieves and removes the first element of this list, or returns null if this list is empty.
  E	pollLast()	Retrieves and removes the last element of this list, or returns null if this list is empty.
  E	pop()	Pops an element from the stack represented by this list.
  void	push​(E e)	Pushes an element onto the stack represented by this list.
  E	remove()	Retrieves and removes the head (first element) of this list.
  E	remove​(int index)	Removes the element at the specified position in this list.
  boolean	remove​(Object o)	Removes the first occurrence of the specified element from this list, if it is present.
  E	removeFirst()	Removes and returns the first element from this list.
  boolean	removeFirstOccurrence​(Object o)	Removes the first occurrence of the specified element in this list (when traversing the list from head to tail).
  E	removeLast()	Removes and returns the last element from this list.
  boolean	removeLastOccurrence​(Object o)	Removes the last occurrence of the specified element in this list (when traversing the list from head to tail).
  E	set​(int index,E element)	Replaces the element at the specified position in this list with the specified element.
  int	size()	Returns the number of elements in this list.
  Spliterator<E>	spliterator()	Creates a late-binding and fail-fast Spliterator over the elements in this list.
  Object[]	toArray()	Returns an array containing all of the elements in this list in proper sequence (from first to last element).
  <T> T[]	toArray​(T[] a)	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

构造方法LinkedList()//创建一个空LinkedList

LinkedList(Coolection<? extends E>)//创建一个有内容的LinkedList，可以将别的LinkedList复制进来（不是引用）

LinkedList增加和删除元素都是常数时间（假设位置已知）

add(int index,E element)向索引位置插入，线性时间

add(E e)默认队尾

addFirst(E e)插入队头

addList(E e)插入队尾

removeFirst(E e)删除队头元素

removeLast(E e)删除队尾元素

LinkedList查询修改元素是线性时间,这点不如ArrayList但是LinkedList的增加和删除是常数时间，不需要移动其他元素的位置。