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Java Source Code / Java Documentation » 6.0 JDK Core » Collections Jar Zip Logging regex » java.util 
Source Cross Reference  Class Diagram Java Document (Java Doc) 


java.util.LinkedList

LinkedList
public class LinkedList extends AbstractSequentialList implements List<E>,Deque<E>,Cloneable,java.io.Serializable(Code)
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, , or .

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 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 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.
author:
   Josh Bloch
version:
   1.73, 05/05/07
See Also:   List
See Also:   ArrayList
See Also:   Vector
since:
   1.2<
Parameters:
  E - > the type of elements held in this collection




Constructor Summary
public  LinkedList()
     Constructs an empty list.
public  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
public  booleanadd(E e)
     Appends the specified element to the end of this list.
public  voidadd(int index, E element)
     Inserts the specified element at the specified position in this list.
public  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.
public  booleanaddAll(int index, Collection<? extends E> c)
     Inserts all of the elements in the specified collection into this list, starting at the specified position.
public  voidaddFirst(E e)
     Inserts the specified element at the beginning of this list.
public  voidaddLast(E e)
     Appends the specified element to the end of this list.
public  voidclear()
     Removes all of the elements from this list.
public  Objectclone()
     Returns a shallow copy of this LinkedList.
public  booleancontains(Object o)
     Returns true if this list contains the specified element.
public  Iterator<E>descendingIterator()
    
public  Eelement()
     Retrieves, but does not remove, the head (first element) of this list.
public  Eget(int index)
     Returns the element at the specified position in this list.
public  EgetFirst()
     Returns the first element in this list.
public  EgetLast()
     Returns the last element in this list.
public  intindexOf(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.
public  intlastIndexOf(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.
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.

public  booleanoffer(E e)
     Adds the specified element as the tail (last element) of this list.
public  booleanofferFirst(E e)
     Inserts the specified element at the front of this list.
public  booleanofferLast(E e)
     Inserts the specified element at the end of this list.
public  Epeek()
     Retrieves, but does not remove, the head (first element) of this list.
public  EpeekFirst()
     Retrieves, but does not remove, the first element of this list, or returns null if this list is empty.
public  EpeekLast()
     Retrieves, but does not remove, the last element of this list, or returns null if this list is empty.
public  Epoll()
    
public  EpollFirst()
     Retrieves and removes the first element of this list, or returns null if this list is empty.
public  EpollLast()
     Retrieves and removes the last element of this list, or returns null if this list is empty.
public  Epop()
     Pops an element from the stack represented by this list.
public  voidpush(E e)
     Pushes an element onto the stack represented by this list.
public  booleanremove(Object o)
     Removes the first occurrence of the specified element from this list, if it is present.
public  Eremove(int index)
     Removes the element at the specified position in this list.
public  Eremove()
     Retrieves and removes the head (first element) of this list.
public  EremoveFirst()
     Removes and returns the first element from this list.
public  booleanremoveFirstOccurrence(Object o)
     Removes the first occurrence of the specified element in this list (when traversing the list from head to tail).
public  EremoveLast()
     Removes and returns the last element from this list.
public  booleanremoveLastOccurrence(Object o)
     Removes the last occurrence of the specified element in this list (when traversing the list from head to tail).
public  Eset(int index, E element)
     Replaces the element at the specified position in this list with the specified element.
public  intsize()
     Returns the number of elements in this list.
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.

public  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.


Constructor Detail
LinkedList
public LinkedList()(Code)
Constructs an empty list.



LinkedList
public LinkedList(Collection<? extends E> c)(Code)
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




Method Detail
add
public boolean add(E e)(Code)
Appends the specified element to the end of this list.

This method is equivalent to LinkedList.addLast .
Parameters:
  e - element to be appended to this list true (as specified by Collection.add)




add
public void add(int index, E element)(Code)
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).
Parameters:
  index - index at which the specified element is to be inserted
Parameters:
  element - element to be inserted
throws:
  IndexOutOfBoundsException -



addAll
public boolean addAll(Collection<? extends E> c)(Code)
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.)
Parameters:
  c - collection containing elements to be added to this list true if this list changed as a result of the call
throws:
  NullPointerException - if the specified collection is null



addAll
public boolean addAll(int index, Collection<? extends E> c)(Code)
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.
Parameters:
  index - index at which to insert the first elementfrom the specified collection
Parameters:
  c - collection containing elements to be added to this list true if this list changed as a result of the call
throws:
  IndexOutOfBoundsException -
throws:
  NullPointerException - if the specified collection is null



addFirst
public void addFirst(E e)(Code)
Inserts the specified element at the beginning of this list.
Parameters:
  e - the element to add



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

This method is equivalent to LinkedList.add .
Parameters:
  e - the element to add




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



clone
public Object clone()(Code)
Returns a shallow copy of this LinkedList. (The elements themselves are not cloned.) a shallow copy of this LinkedList instance



contains
public boolean contains(Object o)(Code)
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)).
Parameters:
  o - element whose presence in this list is to be tested true if this list contains the specified element



descendingIterator
public Iterator<E> descendingIterator()(Code)

since:
   1.6



element
public E element()(Code)
Retrieves, but does not remove, the head (first element) of this list. the head of this list
throws:
  NoSuchElementException - if this list is empty
since:
   1.5



get
public E get(int index)(Code)
Returns the element at the specified position in this list.
Parameters:
  index - index of the element to return the element at the specified position in this list
throws:
  IndexOutOfBoundsException -



getFirst
public E getFirst()(Code)
Returns the first element in this list. the first element in this list
throws:
  NoSuchElementException - if this list is empty



getLast
public E getLast()(Code)
Returns the last element in this list. the last element in this list
throws:
  NoSuchElementException - if this list is empty



indexOf
public int indexOf(Object o)(Code)
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.
Parameters:
  o - element to search for the index of the first occurrence of the specified element inthis list, or -1 if this list does not contain the element



lastIndexOf
public int lastIndexOf(Object o)(Code)
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.
Parameters:
  o - element to search for the index of the last occurrence of the specified element inthis list, or -1 if this list does not contain the element



listIterator
public ListIterator<E> listIterator(int index)(Code)
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.
Parameters:
  index - index of the first element to be returned from thelist-iterator (by a call to next) a ListIterator of the elements in this list (in propersequence), starting at the specified position in the list
throws:
  IndexOutOfBoundsException -
See Also:   List.listIterator(int)




offer
public boolean offer(E e)(Code)
Adds the specified element as the tail (last element) of this list.
Parameters:
  e - the element to add true (as specified by Queue.offer)
since:
   1.5



offerFirst
public boolean offerFirst(E e)(Code)
Inserts the specified element at the front of this list.
Parameters:
  e - the element to insert true (as specified by Deque.offerFirst)
since:
   1.6



offerLast
public boolean offerLast(E e)(Code)
Inserts the specified element at the end of this list.
Parameters:
  e - the element to insert true (as specified by Deque.offerLast)
since:
   1.6



peek
public E peek()(Code)
Retrieves, but does not remove, the head (first element) of this list. the head of this list, or null if this list is empty
since:
   1.5



peekFirst
public E peekFirst()(Code)
Retrieves, but does not remove, the first element of this list, or returns null if this list is empty. the first element of this list, or nullif this list is empty
since:
   1.6



peekLast
public E peekLast()(Code)
Retrieves, but does not remove, the last element of this list, or returns null if this list is empty. the last element of this list, or nullif this list is empty
since:
   1.6



poll
public E poll()(Code)
Retrieves and removes the head (first element) of this list the head of this list, or null if this list is empty
since:
   1.5



pollFirst
public E pollFirst()(Code)
Retrieves and removes the first element of this list, or returns null if this list is empty. the first element of this list, or null ifthis list is empty
since:
   1.6



pollLast
public E pollLast()(Code)
Retrieves and removes the last element of this list, or returns null if this list is empty. the last element of this list, or null ifthis list is empty
since:
   1.6



pop
public E pop()(Code)
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 LinkedList.removeFirst() . the element at the front of this list (which is the topof the stack represented by this list)
throws:
  NoSuchElementException - if this list is empty
since:
   1.6




push
public void push(E e)(Code)
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 LinkedList.addFirst .
Parameters:
  e - the element to push
since:
   1.6




remove
public boolean remove(Object o)(Code)
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).
Parameters:
  o - element to be removed from this list, if present true if this list contained the specified element



remove
public E remove(int index)(Code)
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.
Parameters:
  index - the index of the element to be removed the element previously at the specified position
throws:
  IndexOutOfBoundsException -



remove
public E remove()(Code)
Retrieves and removes the head (first element) of this list. the head of this list
throws:
  NoSuchElementException - if this list is empty
since:
   1.5



removeFirst
public E removeFirst()(Code)
Removes and returns the first element from this list. the first element from this list
throws:
  NoSuchElementException - if this list is empty



removeFirstOccurrence
public boolean removeFirstOccurrence(Object o)(Code)
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 true if the list contained the specified element
since:
   1.6



removeLast
public E removeLast()(Code)
Removes and returns the last element from this list. the last element from this list
throws:
  NoSuchElementException - if this list is empty



removeLastOccurrence
public boolean removeLastOccurrence(Object o)(Code)
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 true if the list contained the specified element
since:
   1.6



set
public E set(int index, E element)(Code)
Replaces the element at the specified position in this list with the specified element.
Parameters:
  index - index of the element to replace
Parameters:
  element - element to be stored at the specified position the element previously at the specified position
throws:
  IndexOutOfBoundsException -



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



toArray
public Object[] toArray()(Code)
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. an array containing all of the elements in this listin proper sequence




toArray
public T[] toArray(T[] a)(Code)
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 LinkedList.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().
Parameters:
  a - the array into which the elements of the list are tobe stored, if it is big enough; otherwise, a new array of thesame runtime type is allocated for this purpose. an array containing the elements of the list
throws:
  ArrayStoreException - if the runtime type of the specified arrayis not a supertype of the runtime type of every element inthis list
throws:
  NullPointerException - if the specified array is null



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