E - the type of elements held in this collectionpublic 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 FormmodCount| Constructor and 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.
|
| 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<? 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.
|
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.
|
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.
|
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, toStringcontainsAll, equals, hashCode, isEmpty, iterator, listIterator, removeAll, retainAll, subListpublic LinkedList()
public LinkedList(Collection<? extends E> c)
c - the collection whose elements are to be placed into this listNullPointerException - if the specified collection is nullpublic 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 listtrue (as specified by Collection.add(E))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 insertedelement - element to be insertedIndexOutOfBoundsException - if the index is out of range (index < 0 || index > size())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 listtrue if this list changed as a result of the callNullPointerException - if the specified collection is nullAbstractCollection.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 collectionc - collection containing elements to be added to this listtrue if this list changed as a result of the callIndexOutOfBoundsException - if the index is out of range (index < 0 || index > size())NullPointerException - if the specified collection is nullpublic void addFirst(E e)
public void addLast(E e)
This method is equivalent to add(E).
public void clear()
clear in interface Collection<E>clear in interface List<E>clear in class AbstractList<E>public Object clone()
LinkedList. (The elements themselves are not cloned.)public boolean contains(Object o)
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 testedtrue if this list contains the specified elementpublic Iterator<E> descendingIterator()
DequedescendingIterator in interface Deque<E>public E element()
public E get(int index)
get in interface List<E>get in class AbstractSequentialList<E>index - index of the element to returnIndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())public E getFirst()
getFirst in interface Deque<E>NoSuchElementException - if this list is emptypublic E getLast()
getLast in interface Deque<E>NoSuchElementException - if this list is emptypublic int indexOf(Object o)
i such that
(o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.public int lastIndexOf(Object o)
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 forpublic 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 boolean offer(E e)
public boolean offerFirst(E e)
offerFirst in interface Deque<E>e - the element to inserttrue (as specified by Deque.offerFirst(E))public boolean offerLast(E e)
offerLast in interface Deque<E>e - the element to inserttrue (as specified by Deque.offerLast(E))@Nullable public E peek()
@Nullable public E peekFirst()
null if this list is empty.@Nullable public E peekLast()
null if this list is empty.@Nullable public E pollFirst()
null if this list is empty.@Nullable public E pollLast()
null if this list is empty.public E pop()
This method is equivalent to removeFirst().
pop in interface Deque<E>NoSuchElementException - if this list is emptypublic void push(E e)
This method is equivalent to addFirst(E).
public E remove()
public E remove(int index)
remove in interface List<E>remove in class AbstractSequentialList<E>index - the index of the element to be removedIndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())public boolean remove(Object o)
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 presenttrue if this list contained the specified elementpublic E removeFirst()
removeFirst in interface Deque<E>NoSuchElementException - if this list is emptypublic boolean removeFirstOccurrence(Object o)
removeFirstOccurrence in interface Deque<E>o - element to be removed from this list, if presenttrue if the list contained the specified elementpublic E removeLast()
removeLast in interface Deque<E>NoSuchElementException - if this list is emptypublic boolean removeLastOccurrence(Object o)
removeLastOccurrence in interface Deque<E>o - element to be removed from this list, if presenttrue if the list contained the specified elementpublic E set(int index, E element)
set in interface List<E>set in class AbstractSequentialList<E>index - index of the element to replaceelement - element to be stored at the specified positionIndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())public int size()
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>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 collectiona - 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 listNullPointerException - if the specified array is null