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General

Linked List in Java

LinkedList Java

LinkedList Java

  • Java LinkedList class uses doubly linked list to store the elements.
  • It provides a linked-list data structure.
  • It inherits AbstractList class and implements List and Deque.
  • LinkedList is better for manipulating elements whereas and ArrayList is best fit for storing and  retrieving the data.

Linked List Types

  • Non generic form of LinkedList
  • Generic form of LinkedList

Non generic form of LinkedList

Syntax:

LinkedList object = new LinkedList(); 

Generic form of LinkedList

Syntax:

LinkedList<DataType> object = new LinkedList<DataType>();

Example:

package Mypkg;
import java.util.Iterator;
import java.util.LinkedList;
public class ListEx {
            /**
             * @param args
             */
            public static void main(String[] args) {
                        // TODO Auto-generated method stub
                        LinkedList<String> li=new LinkedList<String>();// generic collection - FIFO- FCFS- First Come First Serve
                        li.add("Besant");
            li.add("Technologies");
                        li.add("HSR Layout");
                        li.add("Sector-1");
                        li.add("Bangalore");
                        li.addFirst("India");
                        System.out.println("***********************************");
                        System.out.println("List Display" + li.toString());
                        System.out.println("**************************************");
                        li.removeFirst();
                        System.out.println("***********************************");
                        System.out.println("After Removal of First  element" + li.toString());
                        System.out.println("**************************************");
                        li.remove();
                        System.out.println("***********************************");
                        System.out.println("After removal of an element" + li.toString());
                        System.out.println("**************************************");                      
                        li.addFirst("ttttt");                    
                        System.out.println("***********************************");
                        System.out.println("Adding element at first position" +li.toString());
                        System.out.println("**************************************");
                        System.out.println("Get elements of 2nd position " +li.get(2));                       
                        System.out.println("****Linked List items (Foreach Display)****************");
                        for(String d: li)
                        {
                                  System.out.println(d);
                        }                    
                        System.out.println("********************************************************");
                        System.out.println("Linked List (Itertor Display)");
                        Iterator<String> iter=li.iterator();
                        while(iter.hasNext())
                        {
                                    System.out.println(iter.next());
                        }
                        System.out.println("********************************************************");
                        }
}

Output:

***********************************

List Display[India, Besant, Technologies, HSR Layout, Sector-1, Bangalore]

**************************************

***********************************

After Removal of First  element[Besant, Technologies, HSR Layout, Sector-1, Bangalore]

**************************************

***********************************

After removal of an element[Technologies, HSR Layout, Sector-1, Bangalore]

**************************************

***********************************

Adding element at first position[ttttt, Technologies, HSR Layout, Sector-1, Bangalore]

**************************************

Get elements of 2nd position HSR Layout

****Linked List items (Foreach Display)****************

ttttt

Technologies

HSR Layout

Sector-1

Bangalore

********************************************************

Linked List (Itertor Display)

ttttt

Technologies

HSR Layout

Sector-1

Bangalore

********************************************************

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Methods of LinkedList

Method Name Description
boolean add(E e) Appends the element ‘e’ to the end of the list.
void add(int i, E e) Inserts the element ‘e’ at the specified index ‘i’ in the list.
void addFirst(E e) Inserts the element ‘e’ in the start  of the list
void addLast(E e) Inserts the element ‘e’ in the end of the list
void clear() Removes all the elements from the list.
boolean contains(Object o) Returns true if the list contains the object specified in the argument.
E get(int index) Returns the element at the specified index in the list.
boolean isEmpty() Returns true if the list has no elements
E remove(int index) Removes the element at the specified index in the list.
E removeFirst() Removes and returns the first element in the list.
boolean removeFirstOccurence(Object o) Removes the first occurrence of the element in the list.
E removeLast() Removes and returns the last element in the list.
boolean removeLastOccurence(Object o) Removes the last occurrence of the element in the list (traversing from head to tail)
E set(int index, E element) Replaces the element at the specified index in the list with the element given.
int size() Returns the number of elements in the list.
peek() Retrieves the element in the head, but does not remove.
E peekFirst() Retrieves the first element of the list, but does not remove or returns null if this list is empty.
E peekLast() Retrieves the last element of the list, but does not remove or returns null if this list is empty.
E poll() Retrieves and removes the element in the head.
E pollFirst() Retrieves and removes the first element of the list.
E pollLast() Retrieves and removes the last element of the list.
E pop() Pops an element from the list, considering the list as stack.
void push(E e) Inserts the element e to the list, considering the list as stack.
boolean addAll(Collection<? extends E> c) Appends all of the elements in the specified collection to the end of the list.
boolean removeAll(Collection<?> c) Removes all the elements that are contained in the specified collection from the LinkedList.

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