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.
@author Josh Bloch
@version 1.67, 04/21/06
@see List
@see ArrayList
@see Vector
@since 1.2
@param < E> the type of elements held in this collection