- Type Parameters:
E
- the type of elements held in this collection
- All Implemented Interfaces:
Serializable
,Cloneable
,Iterable<E>
,Collection<E>
,Deque<E>
,List<E>
,Queue<E>
,SequencedCollection<E>
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.
- Since:
- 1.2
- See Also:
-
Field Summary
Fields declared in class java.util.AbstractList
modCount
-
Constructor Summary
ConstructorDescriptionConstructs 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
Modifier and TypeMethodDescriptionvoid
Inserts the specified element at the specified position in this list.boolean
Appends the specified element to the end of this list.boolean
addAll
(int index, Collection<? extends E> 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
Inserts the specified element at the beginning of this list.void
Appends the specified element to the end of this list.void
clear()
Removes all of the elements from this list.clone()
Returns a shallow copy of thisLinkedList
.boolean
Returnstrue
if this list contains the specified element.Returns an iterator over the elements in this deque in reverse sequential order.element()
Retrieves, but does not remove, the head (first element) of this list.get
(int index) Returns the element at the specified position in this list.getFirst()
Returns the first element in this list.getLast()
Returns the last element in this list.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.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.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
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
Inserts the specified element at the end of this list.peek()
Retrieves, but does not remove, the head (first element) of this list.Retrieves, but does not remove, the first element of this list, or returnsnull
if this list is empty.peekLast()
Retrieves, but does not remove, the last element of this list, or returnsnull
if this list is empty.poll()
Retrieves and removes the head (first element) of this list.Retrieves and removes the first element of this list, or returnsnull
if this list is empty.pollLast()
Retrieves and removes the last element of this list, or returnsnull
if this list is empty.pop()
Pops an element from the stack represented by this list.void
Pushes an element onto the stack represented by this list.remove()
Retrieves and removes the head (first element) of this list.remove
(int index) Removes the element at the specified position in this list.boolean
Removes the first occurrence of the specified element from this list, if it is present.Removes and returns the first element from this list.boolean
Removes the first occurrence of the specified element in this list (when traversing the list from head to tail).Removes and returns the last element from this list.boolean
Removes the last occurrence of the specified element in this list (when traversing the list from head to tail).reversed()
Returns a reverse-ordered view of this collection.Replaces the element at the specified position in this list with the specified element.int
size()
Returns the number of elements in this list.Creates a late-binding and fail-fastSpliterator
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.Methods declared in class java.util.AbstractSequentialList
iterator
Methods declared in class java.util.AbstractList
equals, hashCode, listIterator, removeRange, subList
Methods declared in class java.util.AbstractCollection
containsAll, isEmpty, removeAll, retainAll, toString
Methods declared in interface java.util.Collection
parallelStream, removeIf, stream, toArray
Methods declared in interface java.util.List
containsAll, equals, hashCode, isEmpty, iterator, listIterator, removeAll, replaceAll, retainAll, sort, subList
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Constructor Details
-
LinkedList
public LinkedList()Constructs an empty list. -
LinkedList
Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.- Parameters:
c
- the collection whose elements are to be placed into this list- Throws:
NullPointerException
- if the specified collection is null
-
-
Method Details
-
getFirst
Returns the first element in this list.- Specified by:
getFirst
in interfaceDeque<E>
- Specified by:
getFirst
in interfaceList<E>
- Specified by:
getFirst
in interfaceSequencedCollection<E>
- Returns:
- the first element in this list
- Throws:
NoSuchElementException
- if this list is empty
-
getLast
-
removeFirst
Removes and returns the first element from this list.- Specified by:
removeFirst
in interfaceDeque<E>
- Specified by:
removeFirst
in interfaceList<E>
- Specified by:
removeFirst
in interfaceSequencedCollection<E>
- Returns:
- the first element from this list
- Throws:
NoSuchElementException
- if this list is empty
-
removeLast
Removes and returns the last element from this list.- Specified by:
removeLast
in interfaceDeque<E>
- Specified by:
removeLast
in interfaceList<E>
- Specified by:
removeLast
in interfaceSequencedCollection<E>
- Returns:
- the last element from this list
- Throws:
NoSuchElementException
- if this list is empty
-
addFirst
-
addLast
-
contains
Returnstrue
if this list contains the specified element. More formally, returnstrue
if and only if this list contains at least one elemente
such thatObjects.equals(o, e)
.- Specified by:
contains
in interfaceCollection<E>
- Specified by:
contains
in interfaceDeque<E>
- Specified by:
contains
in interfaceList<E>
- Overrides:
contains
in classAbstractCollection<E>
- Parameters:
o
- element whose presence in this list is to be tested- Returns:
true
if this list contains the specified element
-
size
-
add
Appends the specified element to the end of this list.This method is equivalent to
addLast(E)
.- Specified by:
add
in interfaceCollection<E>
- Specified by:
add
in interfaceDeque<E>
- Specified by:
add
in interfaceList<E>
- Specified by:
add
in interfaceQueue<E>
- Overrides:
add
in classAbstractList<E>
- Parameters:
e
- element to be appended to this list- Returns:
true
(as specified byCollection.add(E)
)
-
remove
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 indexi
such thatObjects.equals(o, get(i))
(if such an element exists). Returnstrue
if this list contained the specified element (or equivalently, if this list changed as a result of the call).- Specified by:
remove
in interfaceCollection<E>
- Specified by:
remove
in interfaceDeque<E>
- Specified by:
remove
in interfaceList<E>
- Overrides:
remove
in classAbstractCollection<E>
- Parameters:
o
- element to be removed from this list, if present- Returns:
true
if this list contained the specified element
-
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. 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.)- Specified by:
addAll
in interfaceCollection<E>
- Specified by:
addAll
in interfaceDeque<E>
- Specified by:
addAll
in interfaceList<E>
- Overrides:
addAll
in classAbstractCollection<E>
- Parameters:
c
- collection containing elements to be added to this list- Returns:
true
if this list changed as a result of the call- Throws:
NullPointerException
- if the specified collection is null- See Also:
-
addAll
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.- Specified by:
addAll
in interfaceList<E>
- Overrides:
addAll
in classAbstractSequentialList<E>
- Parameters:
index
- index at which to insert the first element from the specified collectionc
- collection containing elements to be added to this list- Returns:
true
if this list changed as a result of the call- Throws:
IndexOutOfBoundsException
- if the index is out of range (index < 0 || index > size()
)NullPointerException
- if the specified collection is null
-
clear
public void clear()Removes all of the elements from this list. The list will be empty after this call returns.- Specified by:
clear
in interfaceCollection<E>
- Specified by:
clear
in interfaceList<E>
- Overrides:
clear
in classAbstractList<E>
-
get
Returns the element at the specified position in this list.- Specified by:
get
in interfaceList<E>
- Overrides:
get
in classAbstractSequentialList<E>
- Parameters:
index
- index of the element to return- Returns:
- the element at the specified position in this list
- Throws:
IndexOutOfBoundsException
- if the index is out of range (index < 0 || index >= size()
)
-
set
Replaces the element at the specified position in this list with the specified element.- Specified by:
set
in interfaceList<E>
- Overrides:
set
in classAbstractSequentialList<E>
- Parameters:
index
- index of the element to replaceelement
- element to be stored at the specified position- Returns:
- the element previously at the specified position
- Throws:
IndexOutOfBoundsException
- if the index is out of range (index < 0 || index >= size()
)
-
add
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).- Specified by:
add
in interfaceList<E>
- Overrides:
add
in classAbstractSequentialList<E>
- Parameters:
index
- index at which the specified element is to be insertedelement
- element to be inserted- Throws:
IndexOutOfBoundsException
- if the index is out of range (index < 0 || index > size()
)
-
remove
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.- Specified by:
remove
in interfaceList<E>
- Overrides:
remove
in classAbstractSequentialList<E>
- Parameters:
index
- the index of the element to be removed- Returns:
- the element previously at the specified position
- Throws:
IndexOutOfBoundsException
- if the index is out of range (index < 0 || index >= size()
)
-
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. More formally, returns the lowest indexi
such thatObjects.equals(o, get(i))
, or -1 if there is no such index. -
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. More formally, returns the highest indexi
such thatObjects.equals(o, get(i))
, or -1 if there is no such index.- Specified by:
lastIndexOf
in interfaceList<E>
- Overrides:
lastIndexOf
in classAbstractList<E>
- Parameters:
o
- element to search for- Returns:
- the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element
-
peek
-
element
-
poll
-
remove
-
offer
-
offerFirst
Inserts the specified element at the front of this list.- Specified by:
offerFirst
in interfaceDeque<E>
- Parameters:
e
- the element to insert- Returns:
true
(as specified byDeque.offerFirst(E)
)- Since:
- 1.6
-
offerLast
Inserts the specified element at the end of this list.- Specified by:
offerLast
in interfaceDeque<E>
- Parameters:
e
- the element to insert- Returns:
true
(as specified byDeque.offerLast(E)
)- Since:
- 1.6
-
peekFirst
-
peekLast
-
pollFirst
-
pollLast
-
push
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
addFirst(E)
. -
pop
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
removeFirst()
.- Specified by:
pop
in interfaceDeque<E>
- Returns:
- 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
-
removeFirstOccurrence
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.- Specified by:
removeFirstOccurrence
in interfaceDeque<E>
- Parameters:
o
- element to be removed from this list, if present- Returns:
true
if the list contained the specified element- Since:
- 1.6
-
removeLastOccurrence
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.- Specified by:
removeLastOccurrence
in interfaceDeque<E>
- Parameters:
o
- element to be removed from this list, if present- Returns:
true
if the list contained the specified element- Since:
- 1.6
-
listIterator
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 ofList.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
remove
oradd
methods, the list-iterator will throw aConcurrentModificationException
. 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.- Specified by:
listIterator
in interfaceList<E>
- Specified by:
listIterator
in classAbstractSequentialList<E>
- Parameters:
index
- index of the first element to be returned from the list-iterator (by a call tonext
)- Returns:
- a ListIterator of the elements in this list (in proper sequence), starting at the specified position in the list
- Throws:
IndexOutOfBoundsException
- if the index is out of range (index < 0 || index > size()
)- See Also:
-
descendingIterator
Description copied from interface:Deque
Returns an iterator over the elements in this deque in reverse sequential order. The elements will be returned in order from last (tail) to first (head).- Specified by:
descendingIterator
in interfaceDeque<E>
- Returns:
- an iterator over the elements in this deque in reverse sequence
- Since:
- 1.6
-
clone
-
toArray
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.
- Specified by:
toArray
in interfaceCollection<E>
- Specified by:
toArray
in interfaceList<E>
- Overrides:
toArray
in classAbstractCollection<E>
- Returns:
- an array containing all of the elements in this list in proper sequence
- See Also:
-
toArray
public <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. 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
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
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
x
is a list known to contain only strings. The following code can be used to dump the list into a newly allocated array ofString
:String[] y = x.toArray(new String[0]);
Note thattoArray(new Object[0])
is identical in function totoArray()
.- Specified by:
toArray
in interfaceCollection<E>
- Specified by:
toArray
in interfaceList<E>
- Overrides:
toArray
in classAbstractCollection<E>
- Type Parameters:
T
- the component type of the array to contain the collection- Parameters:
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.- Returns:
- 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 listNullPointerException
- if the specified array is null
-
spliterator
Creates a late-binding and fail-fastSpliterator
over the elements in this list.The
Spliterator
reportsSpliterator.SIZED
andSpliterator.ORDERED
. Overriding implementations should document the reporting of additional characteristic values.- Specified by:
spliterator
in interfaceCollection<E>
- Specified by:
spliterator
in interfaceIterable<E>
- Specified by:
spliterator
in interfaceList<E>
- Implementation Note:
- The
Spliterator
additionally reportsSpliterator.SUBSIZED
and implementstrySplit
to permit limited parallelism.. - Returns:
- a
Spliterator
over the elements in this list - Since:
- 1.8
-
reversed
Returns a reverse-ordered view of this collection. The encounter order of elements in the returned view is the inverse of the encounter order of elements in this collection. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the collection implementation permits modifications to this view, the modifications "write through" to the underlying collection. Changes to the underlying collection might or might not be visible in this reversed view, depending upon the implementation.Modifications to the reversed view are permitted and will be propagated to this list. In addition, modifications to this list will be visible in the reversed view.
-