- 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>
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:
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Field Summary
Fields declared in class java.util.AbstractList
modCount -
Constructor Summary
ConstructorsConstructorDescriptionConstructs 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 TypeMethodDescriptionvoidInserts the specified element at the specified position in this list.booleanAppends the specified element to the end of this list.booleanaddAll(int index, Collection<? extends E> c) Inserts all of the elements in the specified collection into this list, starting at the specified position.booleanaddAll(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.voidInserts the specified element at the beginning of this list.voidAppends the specified element to the end of this list.voidclear()Removes all of the elements from this list.clone()Returns a shallow copy of thisLinkedList.booleanReturnstrueif 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.intReturns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.intReturns 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.booleanAdds the specified element as the tail (last element) of this list.booleanofferFirst(E e) Inserts the specified element at the front of this list.booleanInserts 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 returnsnullif this list is empty.peekLast()Retrieves, but does not remove, the last element of this list, or returnsnullif 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 returnsnullif this list is empty.pollLast()Retrieves and removes the last element of this list, or returnsnullif this list is empty.pop()Pops an element from the stack represented by this list.voidPushes 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.booleanRemoves the first occurrence of the specified element from this list, if it is present.Removes and returns the first element from this list.booleanRemoves 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.booleanRemoves the last occurrence of the specified element in this list (when traversing the list from head to tail).Replaces the element at the specified position in this list with the specified element.intsize()Returns the number of elements in this list.Creates a late-binding and fail-fastSpliteratorover 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
iteratorMethods declared in class java.util.AbstractList
equals, hashCode, listIterator, removeRange, subListMethods declared in class java.util.AbstractCollection
containsAll, isEmpty, removeAll, retainAll, toStringMethods declared in interface java.util.Collection
parallelStream, removeIf, stream, toArrayMethods declared in interface java.util.List
containsAll, equals, hashCode, isEmpty, iterator, listIterator, removeAll, replaceAll, retainAll, sort, subList
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Constructor Details
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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
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Method Details
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getFirst
Returns the first element in this list.- Specified by:
getFirstin interfaceDeque<E>- Returns:
- the first element in this list
- Throws:
NoSuchElementException- if this list is empty
-
getLast
Returns the last element in this list.- Specified by:
getLastin interfaceDeque<E>- Returns:
- the last element in this list
- Throws:
NoSuchElementException- if this list is empty
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removeFirst
Removes and returns the first element from this list.- Specified by:
removeFirstin interfaceDeque<E>- Returns:
- the first element from this list
- Throws:
NoSuchElementException- if this list is empty
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removeLast
Removes and returns the last element from this list.- Specified by:
removeLastin interfaceDeque<E>- Returns:
- the last element from this list
- Throws:
NoSuchElementException- if this list is empty
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addFirst
Inserts the specified element at the beginning of this list. -
addLast
Appends the specified element to the end of this list.This method is equivalent to
add(E). -
contains
Returnstrueif this list contains the specified element. More formally, returnstrueif and only if this list contains at least one elementesuch thatObjects.equals(o, e).- Specified by:
containsin interfaceCollection<E>- Specified by:
containsin interfaceDeque<E>- Specified by:
containsin interfaceList<E>- Overrides:
containsin classAbstractCollection<E>- Parameters:
o- element whose presence in this list is to be tested- Returns:
trueif this list contains the specified element
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size
public int size()Returns the number of elements in this list. -
add
Appends the specified element to the end of this list.This method is equivalent to
addLast(E).- Specified by:
addin interfaceCollection<E>- Specified by:
addin interfaceDeque<E>- Specified by:
addin interfaceList<E>- Specified by:
addin interfaceQueue<E>- Overrides:
addin classAbstractList<E>- Parameters:
e- element to be appended to this list- Returns:
true(as specified byCollection.add(E))
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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 indexisuch thatObjects.equals(o, get(i))(if such an element exists). Returnstrueif this list contained the specified element (or equivalently, if this list changed as a result of the call).- Specified by:
removein interfaceCollection<E>- Specified by:
removein interfaceDeque<E>- Specified by:
removein interfaceList<E>- Overrides:
removein classAbstractCollection<E>- Parameters:
o- element to be removed from this list, if present- Returns:
trueif this list contained the specified element
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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:
addAllin interfaceCollection<E>- Specified by:
addAllin interfaceDeque<E>- Specified by:
addAllin interfaceList<E>- Overrides:
addAllin classAbstractCollection<E>- Parameters:
c- collection containing elements to be added to this list- Returns:
trueif this list changed as a result of the call- Throws:
NullPointerException- if the specified collection is null- See Also:
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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:
addAllin interfaceList<E>- Overrides:
addAllin 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:
trueif 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
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clear
public void clear()Removes all of the elements from this list. The list will be empty after this call returns.- Specified by:
clearin interfaceCollection<E>- Specified by:
clearin interfaceList<E>- Overrides:
clearin classAbstractList<E>
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get
Returns the element at the specified position in this list.- Specified by:
getin interfaceList<E>- Overrides:
getin 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())
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set
Replaces the element at the specified position in this list with the specified element.- Specified by:
setin interfaceList<E>- Overrides:
setin 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())
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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:
addin interfaceList<E>- Overrides:
addin 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())
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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:
removein interfaceList<E>- Overrides:
removein 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())
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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 indexisuch 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 indexisuch thatObjects.equals(o, get(i)), or -1 if there is no such index.- Specified by:
lastIndexOfin interfaceList<E>- Overrides:
lastIndexOfin 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
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peek
Retrieves, but does not remove, the head (first element) of this list. -
element
Retrieves, but does not remove, the head (first element) of this list. -
poll
Retrieves and removes the head (first element) of this list. -
remove
Retrieves and removes the head (first element) of this list. -
offer
Adds the specified element as the tail (last element) of this list. -
offerFirst
Inserts the specified element at the front of this list.- Specified by:
offerFirstin interfaceDeque<E>- Parameters:
e- the element to insert- Returns:
true(as specified byDeque.offerFirst(E))- Since:
- 1.6
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offerLast
Inserts the specified element at the end of this list.- Specified by:
offerLastin interfaceDeque<E>- Parameters:
e- the element to insert- Returns:
true(as specified byDeque.offerLast(E))- Since:
- 1.6
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peekFirst
Retrieves, but does not remove, the first element of this list, or returnsnullif this list is empty. -
peekLast
Retrieves, but does not remove, the last element of this list, or returnsnullif this list is empty. -
pollFirst
Retrieves and removes the first element of this list, or returnsnullif this list is empty. -
pollLast
Retrieves and removes the last element of this list, or returnsnullif this list is empty. -
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:
popin 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
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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:
removeFirstOccurrencein interfaceDeque<E>- Parameters:
o- element to be removed from this list, if present- Returns:
trueif the list contained the specified element- Since:
- 1.6
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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:
removeLastOccurrencein interfaceDeque<E>- Parameters:
o- element to be removed from this list, if present- Returns:
trueif the list contained the specified element- Since:
- 1.6
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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
removeoraddmethods, 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:
listIteratorin interfaceList<E>- Specified by:
listIteratorin 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:
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descendingIterator
Description copied from interface:DequeReturns 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:
descendingIteratorin interfaceDeque<E>- Returns:
- an iterator over the elements in this deque in reverse sequence
- Since:
- 1.6
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clone
Returns a shallow copy of thisLinkedList. (The elements themselves are not cloned.) -
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:
toArrayin interfaceCollection<E>- Specified by:
toArrayin interfaceList<E>- Overrides:
toArrayin classAbstractCollection<E>- Returns:
- an array containing all of the elements in this list in proper sequence
- See Also:
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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
xis 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:
toArrayin interfaceCollection<E>- Specified by:
toArrayin interfaceList<E>- Overrides:
toArrayin 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
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spliterator
Creates a late-binding and fail-fastSpliteratorover the elements in this list.The
SpliteratorreportsSpliterator.SIZEDandSpliterator.ORDERED. Overriding implementations should document the reporting of additional characteristic values.- Specified by:
spliteratorin interfaceCollection<E>- Specified by:
spliteratorin interfaceIterable<E>- Specified by:
spliteratorin interfaceList<E>- Implementation Note:
- The
Spliteratoradditionally reportsSpliterator.SUBSIZEDand implementstrySplitto permit limited parallelism.. - Returns:
- a
Spliteratorover the elements in this list - Since:
- 1.8
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