Top Description Inners Fields Constructors Methods
java.util

public Class LinkedList<E>

extends AbstractSequentialList<E>
implements List<E>, Deque<E>, Cloneable, Serializable
Class Inheritance
All Implemented Interfaces
java.io.Serializable, java.lang.Cloneable, java.util.Deque, java.util.SequencedCollection, java.util.Collection, java.lang.Iterable, java.util.Queue, java.util.List
Known Direct Subclasses
java.util.LinkedList.ReverseOrderLinkedListView, sun.net.www.http.KeepAliveStreamCleaner
Type Parameters
<E>
the type of elements held in this collection
Imports
java.io.IOException, .ObjectInput, .ObjectOutput, java.util.function.Consumer, .IntFunction, .Predicate, .UnaryOperator, java.util.stream.Stream
Doubly-linked list implementation of the List and Deque interfaces. Implements all optional list operations, and permits all elements (including 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 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 iterator and 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 remove or add methods, the iterator will throw a 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 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
Since
1.2
See Also
List, ArrayList

Nested and Inner Type Summary

Modifier and TypeClass and Description
private class
LinkedList.DescendingIterator

Adapter to provide descending iterators via ListItr.previous

private class
LinkedList.ListItr

pack-priv static class
LinkedList.LLSpliterator<E>

A customized variant of Spliterators.IteratorSpliterator

private static class
LinkedList.Node<E>

pack-priv static class
LinkedList.ReverseOrderLinkedListView<E>

Field Summary

Modifier and TypeField and Description
pack-priv transient LinkedList.Node<E>
first

Pointer to first node.

pack-priv transient LinkedList.Node<E>
last

Pointer to last node.

private static final long
serialVersionUID

pack-priv transient int
size

Constructor Summary

AccessConstructor and Description
public
LinkedList()

Constructs an empty list.

public
LinkedList(Collection<? extends E>
the collection whose elements are to be placed into this list
c)

Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.

Method Summary

Modifier and TypeMethod and Description
public boolean

Returns:

true (as specified by Collection#add)
add(E
element to be appended to this list
e)

Overrides java.util.AbstractList.add.

Implements java.util.List.add, java.util.Deque.add, java.util.Collection.add.

Appends the specified element to the end of this list.

public void
add(int
index at which the specified element is to be inserted
index, E
element to be inserted
element)

Overrides java.util.AbstractSequentialList.add.

Implements java.util.List.add.

Inserts the specified element at the specified position in this list.

public boolean

Returns:

true if this list changed as a result of the call
addAll(Collection<? extends E>
collection containing elements to be added to this list
c)

Overrides java.util.AbstractCollection.addAll.

Implements java.util.List.addAll, java.util.Deque.addAll, java.util.Collection.addAll.

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.

public boolean

Returns:

true if this list changed as a result of the call
addAll(int
index at which to insert the first element from the specified collection
index, Collection<? extends E>
collection containing elements to be added to this list
c)

Overrides java.util.AbstractSequentialList.addAll.

Implements java.util.List.addAll.

Inserts all of the elements in the specified collection into this list, starting at the specified position.

public void
addFirst(E
the element to add
e)

Overrides default java.util.List.addFirst.

Implements java.util.Deque.addFirst.

Inserts the specified element at the beginning of this list.

public void
addLast(E
the element to add
e)

Overrides default java.util.List.addLast.

Implements java.util.Deque.addLast.

Appends the specified element to the end of this list.

private void
checkElementIndex(int index)

private void
checkPositionIndex(int index)

public void
clear()

Overrides java.util.AbstractList.clear.

Implements java.util.List.clear, java.util.Collection.clear.

Removes all of the elements from this list.

public Object

Returns:

a shallow copy of this LinkedList instance
clone()

Overrides java.lang.Object.clone.

Returns a shallow copy of this LinkedList.

public boolean

Returns:

true if this list contains the specified element
contains(Object
element whose presence in this list is to be tested
o)

Overrides java.util.AbstractCollection.contains.

Implements java.util.List.contains, java.util.Deque.contains, java.util.Collection.contains.

Returns true if this list contains the specified element.

public Iterator<E>
descendingIterator()

Implements java.util.Deque.descendingIterator.

Returns an iterator over the elements in this deque in reverse sequential order.

public E

Returns:

the head of this list
element()

Implements java.util.Deque.element.

Retrieves, but does not remove, the head (first element) of this list.

public E

Returns:

the element at the specified position in this list
get(int
index of the element to return
index)

Overrides java.util.AbstractSequentialList.get.

Implements java.util.List.get.

Returns the element at the specified position in this list.

public E

Returns:

the first element in this list
getFirst()

Overrides default java.util.List.getFirst.

Implements java.util.Deque.getFirst.

Returns the first element in this list.

public E

Returns:

the last element in this list
getLast()

Overrides default java.util.List.getLast.

Implements java.util.Deque.getLast.

Returns the last element in this list.

public int

Returns:

the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element
indexOf(Object
element to search for
o)

Overrides java.util.AbstractList.indexOf.

Implements java.util.List.indexOf.

Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.

private boolean
isElementIndex(int index)

Tells if the argument is the index of an existing element.

private boolean
isPositionIndex(int index)

Tells if the argument is the index of a valid position for an iterator or an add operation.

public int

Returns:

the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element
lastIndexOf(Object
element to search for
o)

Overrides java.util.AbstractList.lastIndexOf.

Implements java.util.List.lastIndexOf.

Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.

pack-priv void
linkBefore(E e, LinkedList.Node<E> succ)

Inserts element e before non-null Node succ.

private void
linkFirst(E e)

Links e as first element.

pack-priv void
linkLast(E e)

Links e as last element.

public ListIterator<E>

Returns:

a ListIterator of the elements in this list (in proper sequence), starting at the specified position in the list
listIterator(int
index of the first element to be returned from the list-iterator (by a call to next)
index)

Implements abstract java.util.AbstractSequentialList.listIterator.

Implements java.util.List.listIterator.

Returns a list-iterator of the elements in this list (in proper sequence), starting at the specified position in the list.

pack-priv LinkedList.Node<E>
node(int index)

Returns the (non-null) Node at the specified element index.

public boolean

Returns:

true (as specified by Queue#offer)
offer(E
the element to add
e)

Implements java.util.Deque.offer.

Adds the specified element as the tail (last element) of this list.

public boolean

Returns:

true (as specified by Deque#offerFirst)
offerFirst(E
the element to insert
e)

Implements java.util.Deque.offerFirst.

Inserts the specified element at the front of this list.

public boolean

Returns:

true (as specified by Deque#offerLast)
offerLast(E
the element to insert
e)

Implements java.util.Deque.offerLast.

Inserts the specified element at the end of this list.

private String
outOfBoundsMsg(int index)

Hides java.util.AbstractList.outOfBoundsMsg.

Constructs an IndexOutOfBoundsException detail message.

public E

Returns:

the head of this list, or null if this list is empty
peek()

Implements java.util.Deque.peek.

Retrieves, but does not remove, the head (first element) of this list.

public E

Returns:

the first element of this list, or null if this list is empty
peekFirst()

Implements java.util.Deque.peekFirst.

Retrieves, but does not remove, the first element of this list, or returns null if this list is empty.

public E

Returns:

the last element of this list, or null if this list is empty
peekLast()

Implements java.util.Deque.peekLast.

Retrieves, but does not remove, the last element of this list, or returns null if this list is empty.

public E

Returns:

the head of this list, or null if this list is empty
poll()

Implements java.util.Deque.poll.

Retrieves and removes the head (first element) of this list.

public E

Returns:

the first element of this list, or null if this list is empty
pollFirst()

Implements java.util.Deque.pollFirst.

Retrieves and removes the first element of this list, or returns null if this list is empty.

public E

Returns:

the last element of this list, or null if this list is empty
pollLast()

Implements java.util.Deque.pollLast.

Retrieves and removes the last element of this list, or returns null if this list is empty.

public E

Returns:

the element at the front of this list (which is the top of the stack represented by this list)
pop()

Implements java.util.Deque.pop.

Pops an element from the stack represented by this list.

public void
push(E
the element to push
e)

Implements java.util.Deque.push.

Pushes an element onto the stack represented by this list.

private void
readObject(ObjectInputStream s)

Reconstitutes this LinkedList instance from a stream (that is, deserializes it).

public boolean

Returns:

true if this list contained the specified element
remove(Object
element to be removed from this list, if present
o)

Overrides java.util.AbstractCollection.remove.

Implements java.util.List.remove, java.util.Deque.remove, java.util.Collection.remove.

Removes the first occurrence of the specified element from this list, if it is present.

public E

Returns:

the element previously at the specified position
remove(int
the index of the element to be removed
index)

Overrides java.util.AbstractSequentialList.remove.

Implements java.util.List.remove.

Removes the element at the specified position in this list.

public E

Returns:

the head of this list
remove()

Implements java.util.Deque.remove.

Retrieves and removes the head (first element) of this list.

public E

Returns:

the first element from this list
removeFirst()

Overrides default java.util.List.removeFirst.

Implements java.util.Deque.removeFirst.

Removes and returns the first element from this list.

public boolean

Returns:

true if the list contained the specified element
removeFirstOccurrence(Object
element to be removed from this list, if present
o)

Implements java.util.Deque.removeFirstOccurrence.

Removes the first occurrence of the specified element in this list (when traversing the list from head to tail).

public E

Returns:

the last element from this list
removeLast()

Overrides default java.util.List.removeLast.

Implements java.util.Deque.removeLast.

Removes and returns the last element from this list.

public boolean

Returns:

true if the list contained the specified element
removeLastOccurrence(Object
element to be removed from this list, if present
o)

Implements java.util.Deque.removeLastOccurrence.

Removes the last occurrence of the specified element in this list (when traversing the list from head to tail).

public LinkedList<E>

Returns:

a reverse-ordered view of this collection, as a List
reversed()

Overrides default java.util.List.reversed, java.util.Deque.reversed.

Returns a reverse-ordered view of this collection.

public E

Returns:

the element previously at the specified position
set(int
index of the element to replace
index, E
element to be stored at the specified position
element)

Overrides java.util.AbstractSequentialList.set.

Implements java.util.List.set.

Replaces the element at the specified position in this list with the specified element.

public int

Returns:

the number of elements in this list
size()

Implements abstract java.util.AbstractCollection.size.

Implements java.util.List.size, java.util.Deque.size, java.util.Collection.size.

Returns the number of elements in this list.

public Spliterator<E>

Returns:

a Spliterator over the elements in this list
spliterator()

Overrides default java.util.List.spliterator, java.util.Collection.spliterator.

Creates a late-binding and fail-fast Spliterator over the elements in this list.

private LinkedList<E>
superClone()

public Object[]

Returns:

an array containing all of the elements in this list in proper sequence
toArray()

Overrides java.util.AbstractCollection.toArray.

Implements java.util.List.toArray, java.util.Collection.toArray.

Returns an array containing all of the elements in this list in proper sequence (from first to last element).

public <T> T[]

Returns:

an array containing the elements of the list
toArray(T[]
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.
a)

Overrides java.util.AbstractCollection.toArray.

Implements java.util.List.toArray, java.util.Collection.toArray.

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.

private E
unlinkFirst(LinkedList.Node<E> f)

Unlinks non-null first node f.

private E
unlinkLast(LinkedList.Node<E> l)

Unlinks non-null last node l.

private void
writeObject(ObjectOutputStream s)

Saves the state of this LinkedList instance to a stream (that is, serializes it).

Inherited from java.util.AbstractSequentialList:
iterator