Class LinkedList<E>

java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractList<E>
java.util.AbstractSequentialList<E>
java.util.LinkedList<E>
All Implemented Interfaces:
Iterable<E>, Collection<E>, Deque<E>, List<E>, Queue<E>
public class LinkedList<E> extends AbstractSequentialList<E> implements List<E>, Deque<E>
LinkedList is an implementation of List, backed by a linked list. All optional operations are supported, adding, removing and replacing. The elements can be any objects.
Since:
1.2

  • Field Summary

    Fields inherited from class AbstractList

    modCount

  • Constructor Summary

    Constructors
    Constructor
    Description
    LinkedList()
    Constructs a new empty instance of LinkedList.
    LinkedList(Collection<? extends E> collection)
    Constructs a new instance of LinkedList that holds all of the elements contained in the specified collection.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    add(int location, E object)
    Inserts the specified object into this LinkedList at the specified location.
    boolean
    add(E object)
    Adds the specified object at the end of this LinkedList.
    boolean
    addAll(int location, Collection<? extends E> collection)
    Inserts the objects in the specified collection at the specified location in this LinkedList.
    boolean
    addAll(Collection<? extends E> collection)
    Adds the objects in the specified Collection to this LinkedList.
    void
    addFirst(E object)
    Adds the specified object at the beginning of this LinkedList.
    void
    addLast(E object)
    Adds the specified object at the end of this LinkedList.
    void
    clear()
    Removes all elements from this LinkedList, leaving it empty.
    boolean
    contains(Object object)
    Searches this LinkedList for the specified object.
    Iterator<E>
    descendingIterator()
    Returns the iterator in reverse order, from tail to head.
    E
    element()
    Gets but does not remove the element at the head of the queue.
    E
    get(int location)
    Returns the element at the specified location in this list.
    E
    getFirst()
    Returns the first element in this LinkedList.
    E
    getLast()
    Returns the last element in this LinkedList.
    int
    indexOf(Object object)
    Searches this list for the specified object and returns the index of the first occurrence.
    int
    lastIndexOf(Object object)
    Searches this LinkedList for the specified object and returns the index of the last occurrence.
    ListIterator<E>
    listIterator(int location)
    Returns a ListIterator on the elements of this LinkedList.
    boolean
    offer(E o)
    Inserts the specified element into the queue provided that the condition allows such an operation.
    boolean
    offerFirst(E e)
    Inserts an element at the head of this deque unless it would violate size limit.
    boolean
    offerLast(E e)
    Inserts an element at the tail of this deque unless it would violate size limit.
    E
    peek()
    Gets but does not remove the element at the head of the queue.
    E
    peekFirst()
    Gets but not removes the head element of this deque.
    E
    peekLast()
    Gets but not removes the tail element of this deque.
    E
    poll()
    Gets and removes the element at the head of the queue, or returns null if there is no element in the queue.
    E
    pollFirst()
    Gets and removes the head element of this deque.
    E
    pollLast()
    Gets and removes the tail element of this deque.
    E
    pop()
    Pops the head element of the deque, just same as removeFirst().
    void
    push(E e)
    Pushes the element to the deque(at the head of the deque), just same as addFirst(E).
    E
    remove()
    Gets and removes the element at the head of the queue.
    E
    remove(int location)
    Removes the object at the specified location from this LinkedList.
    boolean
    remove(Object object)
    Removes one instance of the specified object from this Collection if one is contained (optional).
    E
    removeFirst()
    Removes the first object from this LinkedList.
    boolean
    removeFirstOccurrence(Object o)
    Removes the first equivalent element of the specified object.
    E
    removeLast()
    Removes the last object from this LinkedList.
    boolean
    removeLastOccurrence(Object o)
    Removes the last equivalent element of the specified object.
    E
    set(int location, E object)
    Replaces the element at the specified location in this LinkedList with the specified object.
    int
    size()
    Returns the number of elements in this LinkedList.
    Object[]
    toArray()
    Returns a new array containing all elements contained in this LinkedList.
    <T> T[]
    toArray(T[] contents)
    Returns an array containing all elements contained in this LinkedList.

    Methods inherited from class AbstractSequentialList

    iterator

    Methods inherited from class AbstractList

    equals, hashCode, listIterator, removeRange, subList

    Methods inherited from class AbstractCollection

    containsAll, isEmpty, removeAll, retainAll, toString

    Methods inherited from class Object

    clone, getClass, notify, notifyAll, wait, wait, wait

    Methods inherited from interface List

    containsAll, equals, hashCode, isEmpty, iterator, listIterator, removeAll, retainAll, subList

  • Constructor Details

    • LinkedList

      public LinkedList()
      Constructs a new empty instance of LinkedList.

    • LinkedList

      public LinkedList(Collection<? extends E> collection)
      Constructs a new instance of LinkedList that holds all of the elements contained in the specified collection. The order of the elements in this new LinkedList will be determined by the iteration order of collection.
      Parameters:
      collection - the collection of elements to add.

  • Method Details

    • add

      public void add(int location, E object)
      Inserts the specified object into this LinkedList at the specified location. The object is inserted before any previous element at the specified location. If the location is equal to the size of this LinkedList, the object is added at the end.
      Specified by:
      add in interface List<E>
      Overrides:
      add in class AbstractSequentialList<E>
      Parameters:
      location - the index at which to insert.
      object - the object to add.
      Throws:
      IndexOutOfBoundsException - if location < 0 || >= size()

    • add

      public boolean add(E object)
      Adds the specified object at the end of this LinkedList.
      Specified by:
      add in interface Collection<E>
      Specified by:
      add in interface List<E>
      Overrides:
      add in class AbstractList<E>
      Parameters:
      object - the object to add.
      Returns:
      always true

    • addAll

      public boolean addAll(int location, Collection<? extends E> collection)
      Inserts the objects in the specified collection at the specified location in this LinkedList. The objects are added in the order they are returned from the collection's iterator.
      Specified by:
      addAll in interface List<E>
      Overrides:
      addAll in class AbstractSequentialList<E>
      Parameters:
      location - the index at which to insert.
      collection - the collection of objects
      Returns:
      true if this LinkedList is modified, false otherwise.
      Throws:
      ClassCastException - if the class of an object is inappropriate for this list.
      IllegalArgumentException - if an object cannot be added to this list.
      IndexOutOfBoundsException - if location < 0 || > size()

    • addAll

      public boolean addAll(Collection<? extends E> collection)
      Adds the objects in the specified Collection to this LinkedList.
      Specified by:
      addAll in interface Collection<E>
      Specified by:
      addAll in interface List<E>
      Overrides:
      addAll in class AbstractCollection<E>
      Parameters:
      collection - the collection of objects.
      Returns:
      true if this LinkedList is modified, false otherwise.

    • addFirst

      public void addFirst(E object)
      Adds the specified object at the beginning of this LinkedList.
      Specified by:
      addFirst in interface Deque<E>
      Parameters:
      object - the object to add.

    • addLast

      public void addLast(E object)
      Adds the specified object at the end of this LinkedList.
      Specified by:
      addLast in interface Deque<E>
      Parameters:
      object - the object to add.

    • clear

      public void clear()
      Removes all elements from this LinkedList, leaving it empty.
      Specified by:
      clear in interface Collection<E>
      Specified by:
      clear in interface List<E>
      Overrides:
      clear in class AbstractList<E>
      See Also:

    • contains

      public boolean contains(Object object)
      Searches this LinkedList for the specified object.
      Specified by:
      contains in interface Collection<E>
      Specified by:
      contains in interface List<E>
      Overrides:
      contains in class AbstractCollection<E>
      Parameters:
      object - the object to search for.
      Returns:
      true if object is an element of this LinkedList, false otherwise

    • get

      public E get(int location)
      Description copied from class: AbstractList
      Returns the element at the specified location in this list.
      Specified by:
      get in interface List<E>
      Overrides:
      get in class AbstractSequentialList<E>
      Parameters:
      location - the index of the element to return.
      Returns:
      the element at the specified index.

    • getFirst

      public E getFirst()
      Returns the first element in this LinkedList.
      Specified by:
      getFirst in interface Deque<E>
      Returns:
      the first element.
      Throws:
      NoSuchElementException - if this LinkedList is empty.

    • getLast

      public E getLast()
      Returns the last element in this LinkedList.
      Specified by:
      getLast in interface Deque<E>
      Returns:
      the last element
      Throws:
      NoSuchElementException - if this LinkedList is empty

    • indexOf

      public int indexOf(Object object)
      Description copied from class: AbstractList
      Searches this list for the specified object and returns the index of the first occurrence.
      Specified by:
      indexOf in interface List<E>
      Overrides:
      indexOf in class AbstractList<E>
      Parameters:
      object - the object to search for.
      Returns:
      the index of the first occurrence of the object, or -1 if it was not found.

    • lastIndexOf

      public int lastIndexOf(Object object)
      Searches this LinkedList for the specified object and returns the index of the last occurrence.
      Specified by:
      lastIndexOf in interface List<E>
      Overrides:
      lastIndexOf in class AbstractList<E>
      Parameters:
      object - the object to search for
      Returns:
      the index of the last occurrence of the object, or -1 if it was not found.

    • listIterator

      public ListIterator<E> listIterator(int location)
      Returns a ListIterator on the elements of this LinkedList. The elements are iterated in the same order that they occur in the LinkedList. The iteration starts at the specified location.
      Specified by:
      listIterator in interface List<E>
      Specified by:
      listIterator in class AbstractSequentialList<E>
      Parameters:
      location - the index at which to start the iteration
      Returns:
      a ListIterator on the elements of this LinkedList
      Throws:
      IndexOutOfBoundsException - if location < 0 || >= size()
      See Also:

    • remove

      public E remove(int location)
      Removes the object at the specified location from this LinkedList.
      Specified by:
      remove in interface List<E>
      Overrides:
      remove in class AbstractSequentialList<E>
      Parameters:
      location - the index of the object to remove
      Returns:
      the removed object
      Throws:
      IndexOutOfBoundsException - if location < 0 || >= size()

    • remove

      public boolean remove(Object object)
      Description copied from class: AbstractCollection
      Removes one instance of the specified object from this Collection if one is contained (optional). This implementation iterates over this Collection and tests for each element e returned by the iterator, whether e is equal to the given object. If object != null then this test is performed using object.equals(e), otherwise using object == null. If an element equal to the given object is found, then the remove method is called on the iterator and true is returned, false otherwise. If the iterator does not support removing elements, an UnsupportedOperationException is thrown.
      Specified by:
      remove in interface Collection<E>
      Specified by:
      remove in interface List<E>
      Overrides:
      remove in class AbstractCollection<E>
      Parameters:
      object - the object to remove.
      Returns:
      true if this Collection is modified, false otherwise.

    • removeFirst

      public E removeFirst()
      Removes the first object from this LinkedList.
      Specified by:
      removeFirst in interface Deque<E>
      Returns:
      the removed object.
      Throws:
      NoSuchElementException - if this LinkedList is empty.

    • removeLast

      public E removeLast()
      Removes the last object from this LinkedList.
      Specified by:
      removeLast in interface Deque<E>
      Returns:
      the removed object.
      Throws:
      NoSuchElementException - if this LinkedList is empty.

    • descendingIterator

      public Iterator<E> descendingIterator()
      Returns the iterator in reverse order, from tail to head.
      Specified by:
      descendingIterator in interface Deque<E>
      Returns:
      the iterator in reverse order
      Since:
      1.6
      See Also:

    • offerFirst

      public boolean offerFirst(E e)
      Inserts an element at the head of this deque unless it would violate size limit. It is better than the addFirst(E) method in a size-limited deque, because the latter one may fail to add the element only by throwing an exception.
      Specified by:
      offerFirst in interface Deque<E>
      Parameters:
      e - the element
      Returns:
      true if the operation succeeds or false if it fails.
      Since:
      1.6
      See Also:

    • offerLast

      public boolean offerLast(E e)
      Inserts an element at the tail of this deque unless it would violate size limit. It is better than the addLast(E) method in a size-limited deque, because the latter one may fail to add the element only by throwing an exception.
      Specified by:
      offerLast in interface Deque<E>
      Parameters:
      e - the element
      Returns:
      true if the operation succeeds or false if it fails
      Since:
      1.6
      See Also:

    • peekFirst

      public E peekFirst()
      Gets but not removes the head element of this deque. This method returns null if the deque is empty.
      Specified by:
      peekFirst in interface Deque<E>
      Returns:
      the head element or null if the deque is empty
      Since:
      1.6
      See Also:

    • peekLast

      public E peekLast()
      Gets but not removes the tail element of this deque. This method returns null if the deque is empty.
      Specified by:
      peekLast in interface Deque<E>
      Returns:
      the tail element or null if the deque is empty
      Since:
      1.6
      See Also:

    • pollFirst

      public E pollFirst()
      Gets and removes the head element of this deque. This method returns null if the deque is empty.
      Specified by:
      pollFirst in interface Deque<E>
      Returns:
      the head element or null if the deque is empty
      Since:
      1.6
      See Also:

    • pollLast

      public E pollLast()
      Gets and removes the tail element of this deque. This method returns null if the deque is empty.
      Specified by:
      pollLast in interface Deque<E>
      Returns:
      the tail element or null if the deque is empty
      Since:
      1.6
      See Also:

    • pop

      public E pop()
      Pops the head element of the deque, just same as removeFirst().
      Specified by:
      pop in interface Deque<E>
      Returns:
      the head element
      Since:
      1.6
      See Also:

    • push

      public void push(E e)
      Pushes the element to the deque(at the head of the deque), just same as addFirst(E).
      Specified by:
      push in interface Deque<E>
      Parameters:
      e - the element
      Since:
      1.6
      See Also:

    • removeFirstOccurrence

      public boolean removeFirstOccurrence(Object o)
      Removes the first equivalent element of the specified object. If the deque does not contain the element, it is unchanged and returns false.
      Specified by:
      removeFirstOccurrence in interface Deque<E>
      Parameters:
      o - the element to be removed
      Returns:
      true if the operation succeeds or false if the deque does not contain the element.
      Since:
      1.6
      See Also:

    • removeLastOccurrence

      public boolean removeLastOccurrence(Object o)
      Removes the last equivalent element of the specified object. If the deque does not contain the element, it is unchanged and returns false.
      Specified by:
      removeLastOccurrence in interface Deque<E>
      Parameters:
      o - the element to be removed
      Returns:
      true if the operation succeeds or false if the deque does not contain the element.
      Since:
      1.6
      See Also:

    • set

      public E set(int location, E object)
      Replaces the element at the specified location in this LinkedList with the specified object.
      Specified by:
      set in interface List<E>
      Overrides:
      set in class AbstractSequentialList<E>
      Parameters:
      location - the index at which to put the specified object.
      object - the object to add.
      Returns:
      the previous element at the index.
      Throws:
      ClassCastException - if the class of an object is inappropriate for this list.
      IllegalArgumentException - if an object cannot be added to this list.
      IndexOutOfBoundsException - if location < 0 || >= size()

    • size

      public int size()
      Returns the number of elements in this LinkedList.
      Specified by:
      size in interface Collection<E>
      Specified by:
      size in interface List<E>
      Specified by:
      size in class AbstractCollection<E>
      Returns:
      the number of elements in this LinkedList.

    • offer

      public boolean offer(E o)
      Description copied from interface: Queue
      Inserts the specified element into the queue provided that the condition allows such an operation. The method is generally preferable to Collection.add(E), since the latter might throw an exception if the operation fails.
      Specified by:
      offer in interface Queue<E>
      Parameters:
      o - the specified element to insert into the queue.
      Returns:
      true if the operation succeeds and false if it fails.

    • poll

      public E poll()
      Description copied from interface: Queue
      Gets and removes the element at the head of the queue, or returns null if there is no element in the queue.
      Specified by:
      poll in interface Queue<E>
      Returns:
      the element at the head of the queue or null if there is no element in the queue.

    • remove

      public E remove()
      Description copied from interface: Queue
      Gets and removes the element at the head of the queue. Throws a NoSuchElementException if there is no element in the queue.
      Specified by:
      remove in interface Queue<E>
      Returns:
      the element at the head of the queue.

    • peek

      public E peek()
      Description copied from interface: Queue
      Gets but does not remove the element at the head of the queue.
      Specified by:
      peek in interface Queue<E>
      Returns:
      the element at the head of the queue or null if there is no element in the queue.

    • element

      public E element()
      Description copied from interface: Queue
      Gets but does not remove the element at the head of the queue. Throws a NoSuchElementException if there is no element in the queue.
      Specified by:
      element in interface Queue<E>
      Returns:
      the element at the head of the queue.

    • toArray

      public Object[] toArray()
      Returns a new array containing all elements contained in this LinkedList.
      Specified by:
      toArray in interface Collection<E>
      Specified by:
      toArray in interface List<E>
      Overrides:
      toArray in class AbstractList<E>
      Returns:
      an array of the elements from this LinkedList.

    • toArray

      public <T> T[] toArray(T[] contents)
      Returns an array containing all elements contained in this LinkedList. If the specified array is large enough to hold the elements, the specified array is used, otherwise an array of the same type is created. If the specified array is used and is larger than this LinkedList, the array element following the collection elements is set to null.
      Specified by:
      toArray in interface Collection<E>
      Specified by:
      toArray in interface List<E>
      Overrides:
      toArray in class AbstractList<E>
      Parameters:
      contents - the array.
      Returns:
      an array of the elements from this LinkedList.
      Throws:
      ArrayStoreException - if the type of an element in this LinkedList cannot be stored in the type of the specified array.