LinkedList in java

The LinkedList class extends AbstractSequentialList and implements the List interface. It provides a linked-list data structure.

• Java LinkedList class uses doubly linked list to store the elements. It extends the AbstractList class and implements List and Deque interfaces.
• Java LinkedList class can contain duplicate elements.
• Java LinkedList class maintains insertion order.
• Java LinkedList class is non synchronized.
• In Java LinkedList class, manipulation is fast because no shifting needs to be occurred.
• Java LinkedList class can be used as list, stack or queue.

 

 

 

Example of LinkedList in Java

 

import java.util.*;
public class LinkedListExample {
public static void main(String args[]) {

/* Linked List Declaration */
LinkedList<String> linkedlist = new LinkedList<String>();

/*add(String Element) is used for adding
* the elements to the linked list*/
linkedlist.add("Item1");
linkedlist.add("Item5");
linkedlist.add("Item3");
linkedlist.add("Item6");
linkedlist.add("Item2");

/*Display Linked List Content*/
System.out.println("Linked List Content: " +linkedlist);

/*Add First and Last Element*/
linkedlist.addFirst("First Item");
linkedlist.addLast("Last Item");
System.out.println("LinkedList Content after addition: " +linkedlist);

/*This is how to get and set Values*/
Object firstvar = linkedlist.get(0);
System.out.println("First element: " +firstvar);
linkedlist.set(0, "Changed first item");
Object firstvar2 = linkedlist.get(0);
System.out.println("First element after update by set method: " +firstvar2);

/*Remove first and last element*/
linkedlist.removeFirst();
linkedlist.removeLast();
System.out.println("LinkedList after deletion of first and last element: " +linkedlist);

/* Add to a Position and remove from a position*/
linkedlist.add(0, "Newly added item");
linkedlist.remove(2);
System.out.println("Final Content: " +linkedlist);
}
}

Apart from the methods inherited from its parent classes, LinkedList defines following methods:
1 . void add(int index, Object element)
Inserts the specified element at the specified position index in this list. Throws IndexOutOfBoundsException if the specified index is is out of range (index < 0 || index > size()).

2. boolean add(Object o)
Appends the specified element to the end of this list.

3. 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. Throws NullPointerException if the specified collection is null

4. boolean addAll(int index, Collection c)
Inserts all of the elements in the specified collection into this list, starting at the specified position. Throws NullPointerException if the specified collection is null.

5. void addFirst(Object o)
Inserts the given element at the beginning of this list.

6. void addLast(Object o)
Appends the given element to the end of this list.

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

8. Object clone()
Returns a shallow copy of this LinkedList.

9. 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)).

10. Object get(int index)
Returns the element at the specified position in this list. Throws IndexOutOfBoundsException if the specified index is is out of range (index < 0 || index >= size()).

11. Object getFirst()
Returns the first element in this list. Throws NoSuchElementException if this list is empty.

12. Object getLast()
Returns the last element in this list. Throws NoSuchElementException if this list is empty.

13. int indexOf(Object o)
Returns the index in this list of the first occurrence of the specified element, or -1 if the List does not contain this element.

14. int lastIndexOf(Object o)
Returns the index in this list of the last occurrence of the specified element, or -1 if the list does not contain this element.

15. 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. Throws IndexOutOfBoundsException if the specified index is is out of range (index < 0 || index >= size()).

16. Object remove(int index)
Removes the element at the specified position in this list. Throws NoSuchElementException if this list is empty.

17. boolean remove(Object o)
Removes the first occurrence of the specified element in this list. Throws NoSuchElementException if this list is empty. Throws IndexOutOfBoundsException if the specified index is is out of range (index < 0 || index >= size()).

18. Object removeFirst()
Removes and returns the first element from this list. Throws NoSuchElementException if this list is empty.

19. Object removeLast()
Removes and returns the last element from this list. Throws NoSuchElementException if this list is empty.

20. Object set(int index, Object element)
Replaces the element at the specified position in this list with the specified element. Throws IndexOutOfBoundsException if the specified index is is out of range (index < 0 || index >= size()).

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

22. Object[] toArray()
Returns an array containing all of the elements in this list in the correct order. Throws NullPointerException if the specified array is null.

23. Object[] toArray(Object[] a)
Returns an array containing all of the elements in this list in the correct order; the runtime type of the returned array is that of the specified array.