This documentation differs from the official API. Jadeite adds extra features to the API including: variable font sizes, constructions examples, placeholders for classes and methods, and auto-generated “See Also” links. Additionally it is missing some items found in standard Javadoc documentation, including: generics type information, “Deprecated” tags and comments, “See Also” links, along with other minor differences. Please send any questions or feedback to bam@cs.cmu.edu.


java.util
class LinkedList

java.lang.Object extended by java.util.AbstractCollection extended by java.util.AbstractList extended by java.util.AbstractSequentialList extended by java.util.LinkedList
All Implemented Interfaces:
Serializable, Cloneable, Collection, Deque, List

Most common way to construct:

LinkedList A = new LinkedList();

Based on 306 examples


public class LinkedList
extends AbstractSequentialList
implements List, Deque, 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, {@linkplain Queue queue}, or {@linkplain Deque double-ended queue}.

The class implements the Deque interface, providing first-in-first-out queue operations for add, poll, along with other stack and deque 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 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 {@link Collections#synchronizedList 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 {@link 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.


Field Summary
 
Fields inherited from class java.util.AbstractList
modCount
 
Constructor Summary

          Constructs an empty list.

          Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.
 
Method Summary
 boolean

          Appends the specified element to the end of this list.
 void
add(int index, Object element)

          Inserts the specified element at the specified position in this list.
 boolean

          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 c)

          Inserts all of the elements in the specified collection into this list, starting at the specified position.
 void

          Inserts the specified element at the beginning of this list.
 void

          Appends the specified element to the end of this list.
 void

          Removes all of the elements from this list.
 Object

          Returns a shallow copy of this LinkedList.
 boolean

          Returns true if this list contains the specified element.
 Iterator

          
 Object

          Retrieves, but does not remove, the head (first element) of this list.
 Object
get(int index)

          Returns the element at the specified position in this list.
 Object

          Returns the first element in this list.
 Object

          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
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

          Inserts the specified element at the front of this list.
 boolean

          Inserts the specified element at the end of this list.
 Object

          Retrieves, but does not remove, the head (first element) of this list.
 Object

          Retrieves, but does not remove, the first element of this list, or returns null if this list is empty.
 Object

          Retrieves, but does not remove, the last element of this list, or returns null if this list is empty.
 Object

          Retrieves and removes the head (first element) of this list
 Object

          Retrieves and removes the first element of this list, or returns null if this list is empty.
 Object

          Retrieves and removes the last element of this list, or returns null if this list is empty.
 Object
pop()

          Pops an element from the stack represented by this list.
 void

          Pushes an element onto the stack represented by this list.
 Object

          Retrieves and removes the head (first element) of this list.
 Object
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.
 Object

          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).
 Object

          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).
 Object
set(int index, Object element)

          Replaces the element at the specified position in this list with the specified element.
 int

          Returns the number of elements in this list.
 Object[]

          Returns an array containing all of the elements in this list in proper sequence (from first to last element).
 Object[]

          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 inherited from class java.util.AbstractSequentialList
add, addAll, get, iterator, listIterator, remove, set
 
Methods inherited from class java.util.AbstractList
add, add, addAll, clear, equals, get, hashCode, indexOf, iterator, lastIndexOf, listIterator, listIterator, remove, removeRange, set, subList
 
Methods inherited from class java.util.AbstractCollection
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

LinkedList

public LinkedList()
Constructs an empty list.


LinkedList

public LinkedList(Collection 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
Method Detail

add

public boolean add(Object e)
Appends the specified element to the end of this list.

This method is equivalent to {@link #addLast}.

Overrides:
add in class AbstractList
Parameters:
e - element to be appended to this list
Returns:
true (as specified by {@link Collection#add})

add

public void add(int index,
                Object 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).

Overrides:
add in class AbstractSequentialList
Parameters:
index - index at which the specified element is to be inserted
element - element to be inserted

addAll

public boolean addAll(Collection 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. (Note that this will occur if the specified collection is this list, and it's nonempty.)

Overrides:
addAll in class AbstractCollection
Parameters:
c - collection containing elements to be added to this list
Returns:
true if this list changed as a result of the call

addAll

public boolean addAll(int index,
                      Collection 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.

Overrides:
addAll in class AbstractSequentialList
Parameters:
index - index at which to insert the first element from the specified collection
c - collection containing elements to be added to this list
Returns:
true if this list changed as a result of the call

addFirst

public void addFirst(Object e)
Inserts the specified element at the beginning of this list.

Parameters:
e - the element to add

addLast

public void addLast(Object e)
Appends the specified element to the end of this list.

This method is equivalent to {@link #add}.

Parameters:
e - the element to add

clear

public void clear()
Removes all of the elements from this list.

Overrides:
clear in class AbstractList

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

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)).

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

descendingIterator

public Iterator descendingIterator()

element

public Object element()
Retrieves, but does not remove, the head (first element) of this list.

Returns:
the head of this list

get

public Object get(int index)
Returns the element at the specified position in this list.

Overrides:
get in class AbstractSequentialList
Parameters:
index - index of the element to return
Returns:
the element at the specified position in this list

getFirst

public Object getFirst()
Returns the first element in this list.

Returns:
the first element in this list

getLast

public Object getLast()
Returns the last element in this list.

Returns:
the last element in this list

indexOf

public 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. 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.

Overrides:
indexOf in class AbstractList
Parameters:
o - element to search for
Returns:
the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element

lastIndexOf

public 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. 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.

Overrides:
lastIndexOf in class AbstractList
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

listIterator

public 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. 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.

Overrides:
listIterator in class AbstractSequentialList
Parameters:
index - index of the 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

offer

public boolean offer(Object e)
Adds the specified element as the tail (last element) of this list.

Parameters:
e - the element to add
Returns:
true (as specified by {@link Queue#offer})

offerFirst

public boolean offerFirst(Object e)
Inserts the specified element at the front of this list.

Parameters:
e - the element to insert
Returns:
true (as specified by {@link Deque#offerFirst})

offerLast

public boolean offerLast(Object e)
Inserts the specified element at the end of this list.

Parameters:
e - the element to insert
Returns:
true (as specified by {@link Deque#offerLast})

peek

public Object peek()
Retrieves, but does not remove, the head (first element) of this list.

Returns:
the head of this list, or null if this list is empty

peekFirst

public Object peekFirst()
Retrieves, but does not remove, the first element of this list, or returns null if this list is empty.

Returns:
the first element of this list, or null if this list is empty

peekLast

public Object peekLast()
Retrieves, but does not remove, the last element of this list, or returns null if this list is empty.

Returns:
the last element of this list, or null if this list is empty

poll

public Object poll()
Retrieves and removes the head (first element) of this list

Returns:
the head of this list, or null if this list is empty

pollFirst

public Object pollFirst()
Retrieves and removes the first element of this list, or returns null if this list is empty.

Returns:
the first element of this list, or null if this list is empty

pollLast

public Object pollLast()
Retrieves and removes the last element of this list, or returns null if this list is empty.

Returns:
the last element of this list, or null if this list is empty

pop

public Object 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 {@link #removeFirst()}.

Returns:
the element at the front of this list (which is the top of the stack represented by this list)

push

public void push(Object e)
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 {@link #addFirst}.

Parameters:
e - the element to push

remove

public Object remove()
Retrieves and removes the head (first element) of this list.

Returns:
the head of this list

remove

public Object remove(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.

Overrides:
remove in class AbstractSequentialList
Parameters:
index - the index of the element to be removed
Returns:
the element previously at the specified position

remove

public boolean remove(Object o)
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 index 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).

Overrides:
remove in class AbstractCollection
Parameters:
o - element to be removed from this list, if present
Returns:
true if this list contained the specified element

removeFirst

public Object removeFirst()
Removes and returns the first element from this list.

Returns:
the first element from this list

removeFirstOccurrence

public boolean removeFirstOccurrence(Object o)
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.

Parameters:
o - element to be removed from this list, if present
Returns:
true if the list contained the specified element

removeLast

public Object removeLast()
Removes and returns the last element from this list.

Returns:
the last element from this list

removeLastOccurrence

public boolean removeLastOccurrence(Object o)
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.

Parameters:
o - element to be removed from this list, if present
Returns:
true if the list contained the specified element

set

public Object set(int index,
                  Object element)
Replaces the element at the specified position in this list with the specified element.

Overrides:
set in class AbstractSequentialList
Parameters:
index - index of the element to replace
element - element to be stored at the specified position
Returns:
the element previously at the specified position

size

public int size()
Returns the number of elements in this list.

Overrides:
size in class AbstractCollection
Returns:
the number of elements in this list

toArray

public Object[] 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.

Overrides:
toArray in class AbstractCollection
Returns:
an array containing all of the elements in this list in proper sequence

toArray

public Object[] toArray(Object[] 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 {@link #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().

Overrides:
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


This documentation differs from the official API. Jadeite adds extra features to the API including: variable font sizes, constructions examples, placeholders for classes and methods, and auto-generated “See Also” links. Additionally it is missing some items found in standard Javadoc documentation, including: generics type information, “Deprecated” tags and comments, “See Also” links, along with other minor differences. Please send any questions or feedback to bam@cs.cmu.edu.
This page displays the Jadeite version of the documention, which is derived from the offical documentation that contains this copyright notice:
Copyright 2008 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
The official Sun™ documentation can be found here at http://java.sun.com/javase/6/docs/api/.