Java LinkedList

The LinkedList class in Java provides us with the doubly linked list data structure.
Each element of the linked list is known as a node.
Each node points to the address of the next node & its previous node.

Linked lists are preferred over the Array list because the insertion & deletion in the linked lists can be done in a constant time. But, in arrays, if we want to add or delete an element in between then, we need to shift all the other elements.
In a linked list, it is impossible to directly access an element because we need to traverse the whole linked list to get the desired element.

ArrayList Vs. LinkedList :

Although ArrayList & LinkedList both implement the List interface and have the same methods, it is important to understand when to use which one.

The insertion & deletion can be done in constant time in Linked List, so it is best to use the linked list when you need to add or remove elements frequently.
Use ArrayList when you want to access the random elements frequently, as it can’t be done in a linked list in constant time.

Performing various operations on LinkedList :

1. Adding Element in LinkedList:

Similar to ArrayList, add() method is used to add elements in a linked list.
add(Object): Inserts an element at the end of the ArrayList.
add(Index,Object) : Inserts an element at the given index.
Example :

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

        LinkedList<Integer> l1 = new LinkedList<>();

        l1.add(11);
        l1.add(22);
        l1.add(33);
        l1.add(44);
        l1.add(55);
        l1.add(77);
        l1.add(5,77); // Inserts 77 at index 5
        System.out.println("L1 Linked list : "+ l1);

    }
}

Output

L1 Linked list : [11, 22, 33, 44, 55, 77, 77]

2. Removing an element from the LinkedList:

remove() method is used to remove an element from the linked list.
Example :

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

        LinkedList<Integer> l1 = new LinkedList<>();

        l1.add(11);
        l1.add(22);
        l1.add(33);
        l1.add(44);
        l1.add(55);
        l1.add(77);
        l1.add(5,77); 
        System.out.println("L1 Linked list before: "+ l1);

        l1.remove(2); //removes element present at 2nd index
        System.out.println("L1 Linked list after: "  + l1);

    }
}

Output

L1 Linked list before: [11, 22, 33, 44, 55, 77, 77]
L1 Linked list after: [11, 22, 44, 55, 77, 77]

3. Changing An Element Of Linked List :

set() method is used to change an already existing element of a linked list.

Example :

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

        LinkedList<Integer> l1 = new LinkedList<>();

        l1.add(11);
        l1.add(22);
        l1.add(33);
        l1.add(44);
        l1.add(55);
        l1.add(66);
        System.out.println("L1 Linked list before: "+ l1);

        l1.set(2,10); //changes element present at 2nd index (33 changed to 10)
        System.out.println("L1 Linked list after: "  + l1);

    }
}

Output

L1 Linked list before: [11, 22, 33, 44, 55, 66]
L1 Linked list after: [11, 22, 10, 44, 55, 66]

4. Inserting an element at the last of the linked list:

addlast() method is used to insert an element at the start of the linked list.

Example :

F.	import java.util.*;
public class CWH extends Thread{
    public static void main(String[] args) {

        LinkedList<Integer> l1 = new LinkedList<>();

        l1.add(11);
        l1.add(22);
        l1.add(33);
        l1.add(44);
        l1.add(55);
        l1.add(66);
        System.out.println("L1 Linked list before: "+ l1);

        l1.addLast(100); //Inserting 100 at the end of L1
        System.out.println("L1 Linked list after inserting element at last index: "  + l1);

    }
}

Output

L1 Linked list before: [11, 22, 33, 44, 55, 66]
L1 Linked list after inserting element at last index: [11, 22, 33, 44, 55, 66, 100]

5. Inserting an element at the start of the linked list:

addFirst() method is used to insert an element at the start of the linked list.

Example :

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

        LinkedList<Integer> l1 = new LinkedList<>();

        l1.add(11);
        l1.add(22);
        l1.add(33);
        l1.add(44);
        l1.add(55);
        l1.add(66);
        System.out.println("L1 Linked list before: "+ l1);

        l1.addFirst(0); //Inserting 0 at the starting of L1
        System.out.println("L1 Linked list after: "  + l1);

    }
}

Output

L1 Linked list before: [11, 22, 33, 44, 55, 66]
L1 Linked list after: [0, 11, 22, 33, 44, 55, 66]

Examples

package com.company;

import java.util.*;

public class cwh_92_linkedlist {
    public static void main(String[] args) {
        LinkedList<Integer> l1 = new LinkedList<>();
        LinkedList<Integer> l2 = new LinkedList<>();
        l2.add(15);
        l2.add(18);
        l2.add(19);

        l1.add(6);
        l1.add(7);
        l1.add(4);
        l1.add(6);
        l1.add(0, 5);
        l1.add(0, 1);
        l1.addAll(0, l2);
        l1.addLast(676);
        l1.addFirst(788);
        System.out.println(l1.contains(27));
        System.out.println(l1.indexOf(6));
        System.out.println(l1.lastIndexOf(6));
        //l1.clear();
        l1.set(1, 566);
        for(int i=0; i<l1.size(); i++){
            System.out.print(l1.get(i));
            System.out.print(", ");
        }
    }
}

Java LinkedList

ArrayList Vs. LinkedList :

Performing various operations on LinkedList :

1. Adding Element in LinkedList:

Output

2. Removing an element from the LinkedList:

Output

3. Changing An Element Of Linked List :

Output

4. Inserting an element at the last of the linked list:

Output

5. Inserting an element at the start of the linked list:

Output

Examples

Conclusion