E - the type of elements held in this collection
public class LinkedList<E> extends AbstractSequentialList<E> implements List <E>, Deque <E>, Cloneable , Serializable
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.
List,
ArrayList,
Serialized Form
modCount| Constructor and Description |
|---|
LinkedList()
Constructs an empty list.
|
LinkedList(Collection
Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.
|
| Modifier and Type | Method and Description |
|---|---|
boolean |
add(E e)
Appends the specified element to the end of this list.
|
void |
add(int index, E element)
Inserts the specified element at the specified position in this list.
|
boolean |
addAll(Collection
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.
|
boolean |
addAll(int index, Collection
Inserts all of the elements in the specified collection into this list, starting at the specified position.
|
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
Returns
true if this list contains the specified element.
|
Iterator |
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
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
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 |
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
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
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
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 |
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.
|
iteratorequals, hashCode, listIterator, removeRange, subListcontainsAll, isEmpty, removeAll, retainAll, toStringfinalize, getClass, notify, notifyAll, wait, wait, waitcontainsAll, equals, hashCode, isEmpty, iterator, listIterator, removeAll, replaceAll, retainAll, sort, subListparallelStream, removeIf, streampublic LinkedList()
public LinkedList(Collection<? extends E> c)
c - the collection whose elements are to be placed into this list
NullPointerException - if the specified collection is null
public E getFirst()
getFirst in interface
Deque<E>
NoSuchElementException - if this list is empty
public E getLast()
getLast in interface
Deque<E>
NoSuchElementException - if this list is empty
public E removeFirst()
removeFirst in interface
Deque<E>
NoSuchElementException - if this list is empty
public E removeLast()
removeLast in interface
Deque<E>
NoSuchElementException - if this list is empty
public void addFirst(E e)
public void addLast(E e)
This method is equivalent to add(E).
public boolean contains(Objecto)
true if this list contains the specified element. More formally, returns
true if and only if this list contains at least one element
e such that
(o==null ? e==null : o.equals(e)).
contains in interface
Collection<E>
contains in interface
Deque<E>
contains in interface
List<E>
contains in class
AbstractCollection<E>
o - element whose presence in this list is to be tested
true if this list contains the specified element
public int size()
public boolean add(E e)
This method is equivalent to addLast(E).
add in interface
Collection<E>
add in interface
Deque<E>
add in interface
List<E>
add in interface
Queue<E>
add in class
AbstractList<E>
e - element to be appended to this list
true (as specified by
Collection.add(E) )
public boolean remove(Objecto)
i such that
(o==null ? get(i)==null : o.equals(get(i))) (if such an element exists). Returns
true if this list contained the specified element (or equivalently, if this list changed as a result of the call).
remove in interface
Collection<E>
remove in interface
Deque<E>
remove in interface
List<E>
remove in class
AbstractCollection<E>
o - element to be removed from this list, if present
true if this list contained the specified element
public boolean addAll(Collection<? extends E> c)
addAll in interface
Collection<E>
addAll in interface
List<E>
addAll in class
AbstractCollection<E>
c - collection containing elements to be added to this list
true if this list changed as a result of the call
NullPointerException - if the specified collection is null
AbstractCollection.add(Object)
public boolean addAll(int index,
Collection<? extends E> c)
addAll in interface
List<E>
addAll in class
AbstractSequentialList<E>
index - index at which to insert the first element from the specified collection
c - collection containing elements to be added to this list
true if this list changed as a result of the call
IndexOutOfBoundsException - if the index is out of range (
index < 0 || index > size())
NullPointerException - if the specified collection is null
public void clear()
public E get(int index)
get in interface
List<E>
get in class
AbstractSequentialList<E>
index - index of the element to return
IndexOutOfBoundsException - if the index is out of range (
index < 0 || index >= size())
public E set(int index, E element)
set in interface
List<E>
set in class
AbstractSequentialList<E>
index - index of the element to replace
element - element to be stored at the specified position
IndexOutOfBoundsException - if the index is out of range (
index < 0 || index >= size())
public void add(int index,
E element)
add in interface
List<E>
add in class
AbstractSequentialList<E>
index - index at which the specified element is to be inserted
element - element to be inserted
IndexOutOfBoundsException - if the index is out of range (
index < 0 || index > size())
public E remove(int index)
remove in interface
List<E>
remove in class
AbstractSequentialList<E>
index - the index of the element to be removed
IndexOutOfBoundsException - if the index is out of range (
index < 0 || index >= size())
public int indexOf(Objecto)
i such that
(o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.
public int lastIndexOf(Objecto)
i such that
(o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.
lastIndexOf in interface
List<E>
lastIndexOf in class
AbstractList<E>
o - element to search for
public E peek()
public E element()
public E poll()
public E remove()
public boolean offer(E e)
public boolean offerFirst(E e)
offerFirst in interface
Deque<E>
e - the element to insert
true (as specified by
Deque.offerFirst(E) )
public boolean offerLast(E e)
offerLast in interface
Deque<E>
e - the element to insert
true (as specified by
Deque.offerLast(E) )
public E peekFirst()
null if this list is empty.
public E peekLast()
null if this list is empty.
public E pollFirst()
null if this list is empty.
public E pollLast()
null if this list is empty.
public void push(E e)
This method is equivalent to addFirst(E).
public E pop()
This method is equivalent to removeFirst().
pop in interface
Deque<E>
NoSuchElementException - if this list is empty
public boolean removeFirstOccurrence(Objecto)
removeFirstOccurrence in interface
Deque<E>
o - element to be removed from this list, if present
true if the list contained the specified element
public boolean removeLastOccurrence(Objecto)
removeLastOccurrence in interface
Deque<E>
o - element to be removed from this list, if present
true if the list contained the specified element
public ListIterator<E> listIterator(int index)
List.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 or add methods, the list-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.
listIterator in interface
List<E>
listIterator in class
AbstractSequentialList<E>
index - index of the first element to be returned from the list-iterator (by a call to
next)
IndexOutOfBoundsException - if the index is out of range (
index < 0 || index > size())
List.listIterator(int)
public Iterator<E> descendingIterator()
Deque
descendingIterator in interface
Deque<E>
public Objectclone()
LinkedList. (The elements themselves are not cloned.)
public Object[] toArray()
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.
toArray in interface
Collection<E>
toArray in interface
List<E>
toArray in class
AbstractCollection<E>
Arrays.asList(Object[])
public <T> T[] toArray(T[] a)
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 of String:
String[] y = x.toArray(new String[0]); Note that
toArray(new Object[0]) is identical in function to
toArray().
toArray in interface
Collection<E>
toArray in interface
List<E>
toArray in class
AbstractCollection<E>
T - the runtime type of the array to contain the collection
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.
ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this list
NullPointerException - if the specified array is null
public Spliterator<E> spliterator()
Spliterator over the elements in this list.
The Spliterator reports Spliterator and Spliterator. Overriding implementations should document the reporting of additional characteristic values.
spliterator in interface
Iterable<E>
spliterator in interface
Collection<E>
spliterator in interface
List<E>
Spliterator over the elements in this list