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java.util
Class
LinkedList<E>
LinkedList
java.lang.Object
java.util.AbstractCollection
java.util.AbstractList
java.util.AbstractSequentialList
java.util.LinkedList
-
-
Type Parameters:
All Implemented Interfaces:
-
E - the type of elements held in this collection
Cloneable
,
Collection
,
List
,
Serializable
-
All Implemented Interfaces:
-
Cloneable
,
Collection
,
Iterable
,
List
,
Queue
,
Serializable
-
public class
LinkedList<E>
LinkedList
-
extends
AbstractSequentialList
<E>
-
implements
List
<E>,
Queue
,
Cloneable
<E>,
Cloneable
,
Serializable
Linked list implementation of the
List
interface. Implements all optional list operations, and permits all elements (including
null
). In addition to implementing the
List
interface, the
LinkedList
class provides uniformly named methods to
get
,
remove
and
insert
an element at the beginning and end of the list. These operations allow linked lists to be used as a stack, queue, or double-ended queue (deque).
The class implements the
Queue
interface, providing first-in-first-out queue operations for
add
,
poll
, etc. Other stack and deque operations could be easily recast in terms of the standard list operations.
All of the stack/queue/deque operations could be easily recast in terms of the standard list operations.
They're included here primarily for convenience, though they may run slightly faster than the equivalent List operations.
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
begining
or the end, whichever is closer to the specified index.
Note that this implementation is not synchronized.
If multiple threads access a 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 the 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:
-
List
,
ArrayList
,
Vector
,
Collections.synchronizedList(List)
,
Serialized Form
Constructor Summary
|
LinkedList
()
Constructs an empty list. |
LinkedList
(
Collection
<? extends
E
Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator. |
Method Summary
|
boolean
void
|
add
add
(
E
(int index,
Object
Appends
Inserts
the specified element
to
at
the
end of
specified position in
this list. |
void
boolean
|
add
add
(int index,
E
(
Object
Inserts
Appends
the specified element
at
to
the
specified position in
end of
this list. |
boolean |
addAll
(
Collection
<? extends
E
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
Inserts all of the elements in the specified collection into this list, starting at the specified position. |
void |
addFirst
addFirst
(
E
Object
Inserts the given element at the beginning of this list. |
void |
addLast
addLast
(
E
Object
Appends the given 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. |
E
Object
|
element
get
()
(int index)
Retrieves, but does not remove,
Returns
the
head (first element) of
element at the specified position in
this list. |
E
Object
|
get
getFirst
(int index)
()
Returns the
first
element
at the specified position
in this list. |
E
Object
|
getFirst
getLast
()
Returns the
first
last
element in this list. |
E
|
getLast
()
Returns the last element in this list.
|
int |
indexOf
(
Object
o)
Returns the index in this list of the first occurrence of the specified element, or -1 if the List does not contain this element. |
int |
lastIndexOf
(
Object
o)
Returns the index in this list of the last occurrence of the specified element, or -1 if the list does not contain this 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
Object
|
offer
remove
(
E
(int index)
Adds
Removes
the
specified
element
as
at
the
tail (last element) of
specified position in
this list. |
E
|
peek
()
Retrieves, but does not remove, the head (first element) of this list.
|
E
|
poll
()
Retrieves and removes the head (first element) of 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 in this list. |
E
Object
|
removeFirst
()
Removes and returns the first element from this list. |
E
Object
|
removeLast
()
Removes and returns the last element from this list. |
E
Object
|
set
set
(int index,
E
Object
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 the correct order. |
<T> T[]
|
Object
|
toArray
(
Object
Returns an array containing all of the elements in this list in the correct order; the runtime type of the returned array is that of the specified array.
|
|
toArray
(T[] a)
Returns an array containing all of the elements in this list in the correct order; the runtime type of the returned array is that of the specified array.
|
LinkedList
public LinkedList()
-
Constructs an empty list.
LinkedList
public LinkedList(Collection<? extends E> c) c)
-
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.
getFirst
public EObjectgetFirst()
-
Returns the first element in this list.
-
-
-
Returns:
-
the first element in this list.
-
Throws:
-
NoSuchElementException
- if this list is empty.
getLast
public EObjectgetLast()
-
Returns the last element in this list.
-
-
-
Returns:
-
the last element in this list.
-
Throws:
-
NoSuchElementException
- if this list is empty.
removeFirst
public EObjectremoveFirst()
-
Removes and returns the first element from this list.
-
-
-
Returns:
-
the first element from this list.
-
Throws:
-
NoSuchElementException
- if this list is empty.
removeLast
public EObjectremoveLast()
-
Removes and returns the last element from this list.
-
-
-
Returns:
-
the last element from this list.
-
Throws:
-
NoSuchElementException
- if this list is empty.
addFirst
public void addFirst( EObject o)
-
Inserts the given element at the beginning of this list.
-
-
-
Parameters:
-
o - the element to be inserted at the beginning of this list.
addLast
public void addLast( EObject o)
-
Appends the given element to the end of this list. (Identical in function to the
add
method; included only for consistency.)
-
-
-
Parameters:
-
o - the element to be inserted at the end of this list.
contains
public boolean contains(Object o)
-
Returns
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))
.
-
-
Specified by:
-
contains
in interface
List
-
Overrides:
-
contains
in class
AbstractCollection
-
-
Parameters:
-
o - element whose presence in this list is to be tested.
-
Returns:
-
true
if this list contains the specified element.
size
public int size()
-
Returns the number of elements in this list.
-
-
Specified by:
-
size
in interface
List
-
Specified by:
-
size
in class
AbstractCollection
-
-
Returns:
-
the number of elements in this list.
add
public boolean add( EObject o)
-
Appends the specified element to the end of this list.
-
-
Specified by:
-
add
add
in interface
List
-
Overrides:
-
add
add
in class
AbstractList
-
-
Parameters:
-
o - element to be appended to this list.
-
Returns:
-
true
(as per the general contract of
Collection.add
).
remove
public boolean remove(Object o)
-
Removes the first occurrence of the specified element in this list. If the list does not contain the element, it is unchanged. More formally, removes the element with the lowest index
i
such that
(o==null ? get(i)==null : o.equals(get(i)))
(if such an element exists).
-
-
Specified by:
-
remove
in interface
List
-
Overrides:
-
remove
in class
AbstractCollection
-
-
Parameters:
-
o - element to be removed from this list, if present.
-
Returns:
-
true
if the list contained the specified element.
addAll
public boolean addAll(Collection<? extends E> c) 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. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. (This implies that the behavior of this call is undefined if the specified Collection is this list, and this list is nonempty.)
-
-
Specified by:
-
addAll
in interface
List
-
Overrides:
-
addAll
in class
AbstractCollection
-
-
Parameters:
-
c - the elements to be inserted into this list.
-
Returns:
-
true
if this list changed as a result of the call.
-
Throws:
-
NullPointerException
- if the specified collection is null.
-
See Also:
-
AbstractCollection.add(Object)
AbstractCollection.add(Object)
addAll
public boolean addAll(int index,
Collection<? extends E> c) c)
-
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 interface
List
-
Overrides:
-
addAll
in class
AbstractSequentialList
-
-
Parameters:
-
index - index at which to insert first element from the specified collection.
-
c - elements to be inserted into this list.
-
Returns:
-
true
if this list changed as a result of the call.
-
Throws:
-
IndexOutOfBoundsException
- if the specified 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.
-
-
Specified by:
-
clear
in interface
List
-
Overrides:
-
clear
in class
AbstractList
-
get
public EObjectget(int index)
-
Returns the element at the specified position in this list.
-
-
Specified by:
-
get
in interface
List
-
Overrides:
-
get
in class
AbstractSequentialList
-
-
Parameters:
-
index - index of element to return.
-
Returns:
-
the element at the specified position in this list.
-
Throws:
-
IndexOutOfBoundsException
- if the specified index is is out of range (
index < 0 || index >= size()
).
set
public EObjectset(int index,
EObject element)
-
Replaces the element at the specified position in this list with the specified element.
-
-
Specified by:
-
set
set
in interface
List
-
Overrides:
-
set
set
in class
AbstractSequentialList
-
-
Parameters:
-
index - index of element to replace.
-
element - element to be stored at the specified position.
-
Returns:
-
the element previously at the specified position.
-
Throws:
-
IndexOutOfBoundsException
- if the specified index is out of range (
index < 0 || index >= size()
).
add
public void add(int index,
EObject element)
-
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
add
in interface
List
-
Overrides:
-
add
add
in class
AbstractSequentialList
-
-
Parameters:
-
index - index at which the specified element is to be inserted.
-
element - element to be inserted.
-
Throws:
-
IndexOutOfBoundsException
- if the specified index is out of range (
index < 0 || index > size()
).
remove
public EObjectremove(int index)
-
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 interface
List
-
Overrides:
-
remove
in class
AbstractSequentialList
-
-
Parameters:
-
index - the index of the element to removed.
-
Returns:
-
the element previously at the specified position.
-
Throws:
-
IndexOutOfBoundsException
- if the specified index is out of range (
index < 0 || index >= size()
).
indexOf
public int indexOf(Object o)
-
Returns the index in this list of the first occurrence of the specified element, or -1 if the List does not contain this element. More formally, returns the lowest index i such that
(o==null ? get(i)==null : o.equals(get(i)))
, or -1 if there is no such index.
-
-
Specified by:
-
indexOf
in interface
List
-
Overrides:
-
indexOf
in class
AbstractList
-
-
Parameters:
-
o - element to search for.
-
Returns:
-
the index in this list of the first occurrence of the specified element, or -1 if the list does not contain this element.
lastIndexOf
public int lastIndexOf(Object o)
-
Returns the index in this list of the last occurrence of the specified element, or -1 if the list does not contain this element. More formally, returns the highest index i such that
(o==null ? get(i)==null : o.equals(get(i)))
, or -1 if there is no such index.
-
-
Specified by:
-
lastIndexOf
in interface
List
-
Overrides:
-
lastIndexOf
in class
AbstractList
-
-
Parameters:
-
o - element to search for.
-
Returns:
-
the index in this list of the last occurrence of the specified element, or -1 if the list does not contain this element.
peek
public Epeek ()
-
Retrieves, but does not remove, the head (first element) of this list.
-
-
Specified by:
-
peek
in interface
Queue
-
-
Returns:
-
the head of this queue, or
null
if this queue is empty.
-
Since:
-
1.5
element
public Eelement ()
-
Retrieves, but does not remove, the head (first element) of this list.
-
-
Specified by:
-
element
in interface
Queue
-
-
Returns:
-
the head of this queue.
-
Throws:
-
NoSuchElementException
- if this queue is empty.
-
Since:
-
1.5
poll
public Epoll ()
-
Retrieves and removes the head (first element) of this list.
-
-
Specified by:
-
poll
in interface
Queue
-
-
Returns:
-
the head of this queue, or
null
if this queue is empty.
-
Since:
-
1.5
remove
public Eremove ()
-
Retrieves and removes the head (first element) of this list.
-
-
Specified by:
-
remove
in interface
Queue
-
-
Returns:
-
the head of this queue.
-
Throws:
-
NoSuchElementException
- if this queue is empty.
-
Since:
-
1.5
offer
public boolean offer ( E o)
-
Adds the specified element as the tail (last element) of this list.
-
-
Specified by:
-
offer
in interface
Queue
-
-
Parameters:
-
o - the element to add.
-
Returns:
-
true
(as per the general contract of
Queue.offer
)
-
Since:
-
1.5
listIterator
public 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. Obeys the general contract of
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.
-
-
Specified by:
-
listIterator
in interface
List
-
Specified by:
-
listIterator
in class
AbstractSequentialList
-
-
Parameters:
-
index - index of first element to be returned from the list-iterator (by a call to
next
).
-
Returns:
-
a ListIterator of the elements in this list (in proper sequence), starting at the specified position in the list.
-
Throws:
-
IndexOutOfBoundsException
- if index is out of range (
index < 0 || index > size()
).
-
See Also:
-
List.listIterator(int)
clone
public Object clone()
-
Returns a shallow copy of this
LinkedList
. (The elements themselves are not cloned.)
-
-
Overrides:
-
clone
in class
Object
-
-
Returns:
-
a shallow copy of this
LinkedList
instance.
-
See Also:
-
Cloneable
toArray
public Object[] toArray()
-
Returns an array containing all of the elements in this list in the correct order.
-
-
Specified by:
-
toArray
in interface
List
-
Overrides:
-
toArray
in class
AbstractCollection
-
-
Returns:
-
an array containing all of the elements in this list in the correct order.
-
See Also:
-
Arrays.asList(Object[])
Arrays.asList(Object[])
toArray
public <T> T[]
public Object[] toArray(T[] a) ( Object[] a)
-
Returns an array containing all of the elements in this list in the correct order; 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 collection 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.
-
-
Specified by:
-
toArray
toArray
in interface
List
-
Overrides:
-
toArray
toArray
in class
AbstractCollection
-
-
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 a is not a supertype of the runtime type of every element in this list.
-
NullPointerException
- if the specified array is null.