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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 |
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Fields inherited from class java.util.AbstractList |
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modCount |
Constructor Summary | |
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Constructs an empty list. |
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Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator. |
Method Summary | |
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boolean |
Appends the specified element to the end of this list. |
void |
Inserts the specified element at the specified position in this list. |
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. |
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 |
clear() Removes all of the elements from this list. |
Object |
clone() Returns a shallow copy of this LinkedList. |
boolean |
Returns true if this list contains the specified element. |
Iterator |
|
Object |
element() 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 |
getFirst() Returns the first element in this list. |
Object |
getLast() 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 |
offerFirst(Object e) Inserts the specified element at the front of this list. |
boolean |
Inserts the specified element at the end of this list. |
Object |
peek() 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 |
peekLast() Retrieves, but does not remove, the last element of this list, or returns null if this list is empty. |
Object |
poll() 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 |
pollLast() 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 |
remove() 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 |
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 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 |
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add, addAll, get, iterator, listIterator, remove, set |
Methods inherited from class java.util.AbstractList |
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add, add, addAll, clear, equals, get, hashCode, indexOf, iterator, lastIndexOf, listIterator, listIterator, remove, removeRange, set, subList |
Methods inherited from class java.util.AbstractCollection |
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add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toString |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public LinkedList()
public LinkedList(Collection c)
c
- the collection whose elements are to be placed into this listMethod Detail |
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public boolean add(Object e)
This method is equivalent to {@link #addLast}.
add
in class AbstractList
e
- element to be appended to this listpublic void add(int index, Object element)
add
in class AbstractSequentialList
index
- index at which the specified element is to be insertedelement
- element to be insertedpublic boolean addAll(Collection c)
addAll
in class AbstractCollection
c
- collection containing elements to be added to this listpublic boolean addAll(int index, Collection c)
addAll
in class AbstractSequentialList
index
- index at which to insert the first element
from the specified collectionc
- collection containing elements to be added to this listpublic void addFirst(Object e)
e
- the element to addpublic void addLast(Object e)
This method is equivalent to {@link #add}.
e
- the element to addpublic void clear()
clear
in class AbstractList
public Object clone()
clone
in class Object
public boolean contains(Object o)
contains
in class AbstractCollection
o
- element whose presence in this list is to be testedpublic Iterator descendingIterator()
public Object element()
public Object get(int index)
get
in class AbstractSequentialList
index
- index of the element to returnpublic Object getFirst()
public Object getLast()
public int indexOf(Object o)
indexOf
in class AbstractList
o
- element to search forpublic int lastIndexOf(Object o)
lastIndexOf
in class AbstractList
o
- element to search forpublic ListIterator listIterator(int index)
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.
listIterator
in class AbstractSequentialList
index
- index of the first element to be returned from the
list-iterator (by a call to next)public boolean offer(Object e)
e
- the element to addpublic boolean offerFirst(Object e)
e
- the element to insertpublic boolean offerLast(Object e)
e
- the element to insertpublic Object peek()
public Object peekFirst()
public Object peekLast()
public Object poll()
public Object pollFirst()
public Object pollLast()
public Object pop()
This method is equivalent to {@link #removeFirst()}.
public void push(Object e)
This method is equivalent to {@link #addFirst}.
e
- the element to pushpublic Object remove()
public Object remove(int index)
remove
in class AbstractSequentialList
index
- the index of the element to be removedpublic boolean remove(Object o)
remove
in class AbstractCollection
o
- element to be removed from this list, if presentpublic Object removeFirst()
public boolean removeFirstOccurrence(Object o)
o
- element to be removed from this list, if presentpublic Object removeLast()
public boolean removeLastOccurrence(Object o)
o
- element to be removed from this list, if presentpublic Object set(int index, Object element)
set
in class AbstractSequentialList
index
- index of the element to replaceelement
- element to be stored at the specified positionpublic int size()
size
in class AbstractCollection
public Object[] toArray()
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.
toArray
in class AbstractCollection
public Object[] toArray(Object[] a)
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().
toArray
in class AbstractCollection
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.
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