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How to reverse a linked list in Java

Vinisha Maheshwari

The process of reversing a linked list involves reversing the order of its data nodes. As a result, the last node becomes the head node, and the head node becomes the last node of the original linked list.

Example

Suppose you have a linked list consisting of the following data nodes:

115566994422

Currently, the node with the value 1 is at the head of the list. The order of the nodes after the reversal process is shown below:

224499665511

After the reversal, the node with value 2 is at the head.

Solution approach

You can use the Collections.reverse() method from the java.util package to reverse the order of elements in a list.

The Collections.reverse() method accepts the following parameter:

  • list: This is the linked list that we want to reverse.

Code

The code snippet below shows how to reverse a linked list in Java:

import java.util.*;
class Main 
{
    public static void main(String[] args)
    {
        LinkedList<Integer> list = new LinkedList<Integer>();
        Scanner sc=new Scanner(System.in);
        
        list.add(3);
        list.add(25);
        list.add(14);
        list.add(16);
        list.add(9);
        
        System.out.println("Original linked list: " + list);
        Collections.reverse(list);
        System.out.println("Reversed linked list: " + list);
    }
}

Explanation

  • In line 1 we have imported the required package.

  • In line 2 we have initiated a class Main.

  • In line 6 we have declared a linked list of int data type.

  • In line 7 we have initiated an object as Scanner class to use the methods available in it.

  • In lines 9 to 13 we have taken input of data from every node.

  • In line 15 we display the originally input linked list.

  • In line 16 we used the reverse() method of the collections class from the java.util package to reverse the list.

  • In line 17 we display the reversed linked list.

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