Java Program to Convert the LinkedList into an Array and vice versa

May 27, 2023

What is LinkedList ?

In this Article, We will going to write a Program to Convert the LinkedList into an Array and vice versa.

A linked list is a linear data structure in which each element (called a node) stores a reference to the next element in the list. Linked lists are dynamic data structures, which means that their size can change during the execution of a program. In contrast, arrays have a fixed size, which means that you need to specify the size of the array when you create it and you cannot change it later.

Algorithm to Convert the LinkedList into an Array:

Create an empty array.
Set the current node of the linked list to the head node.
Traverse the linked list using a loop until the current node is null.
At each node, add the node’s value to the end of the array using the array’s “push” method.
Set the current node to the next node in the linked list.
When the loop is finished, the array will contain all the values from the linked list.

Pseudo Code:

// function definition
function linkedListToArray(head){
  // Array Initialization    
  const arr = [];
  let current = head;
  
  // loop to convert linkedlist to array
  while (current !== null) {
    arr.push(current.val);
    current = current.next;
  }
  
  // returning the array
  return arr;
}

Example:

Run

// importing all the required packages
import java.util.LinkedList;

public class Main{
    public static void main(String[] args){
        // Create a linked list
        LinkedList linkedList = new LinkedList();
        
        // Adding elements to a Linkedlist
        linkedList.add(10);
        linkedList.add(20);
        linkedList.add(30);
        linkedList.add(40);
        linkedList.add(50);

        // Convert the linked list to an array
        Integer[] array = linkedList.toArray(new Integer[linkedList.size()]);

        // Print the array
        for (int i = 0; i < array.length; i++) {
            System.out.print(array[i] + " ");
        }
    }
}

Output:

10 20 30 40 50

Explanation: The above program creates a linked list of integers using the LinkedList class from the Java standard library. It adds some values to the linked list. Then, it converts the linked list to an array using the toArray() method of the LinkedList class. Finally, it prints the resulting array using a loop.

Algorithm to Convert the Array into an LinkedList:

Create a new head node and set it to null.
Loop through the array in reverse order (starting from the last element).
For each element in the array, create a new node and set its value to the current element.
Set the “next” pointer of the new node to the current head node.
Set the new node as the new head node.
When the loop is finished, the new head node will be the first node in the linked list.

Pseudo Code:

// Function definition
function arrayToLinkedList(arr) {
  Node head = null;
  
  // loop to convert array to linkedlist
  for (int i = arr.length - 1; i >= 0; i--) {
    Node newNode = new Node(arr[i]);
    newNode.next = head;
    head = newNode;
  }
  return head;
}

Example:

Run

// importing all the required packages
import java.util.*;

public class Main {
    public static void main(String[] args) {
        // Create an integer array
        int[] arr = {10, 20, 30, 40, 50};

        // Convert the array to a linked list
        Node head = arrayToLinkedList(arr);

        // Print the linked list
        printLinkedList(head);
    }

    // Function definition
    public static Node arrayToLinkedList(int[] arr) {
        Node head = null;
        for (int i = arr.length - 1; i >= 0; i--) {
            Node newNode = new Node(arr[i]);
            newNode.next = head;
            head = newNode;
        }
        return head;
    }

    // Print function
    public static void printLinkedList(Node head) {
        while (head != null) {
            System.out.print(head.val + " ");
            head = head.next;
        }
    }
}

// Node class
class Node {
    int val;
    Node next;

    public Node(int val) {
        this.val = val;
    }
}

Output:

10 20 30 40 50

Explanation: The above program creates an integer array and then converts it to a linked list using the arrayToLinkedList() method. It then prints the resulting linked list using the printLinkedList() method. Note that the Node class is defined in the program as an inner class of the ArrayToLinkedList class.

Prime Course Trailer

Related Banners

Get PrepInsta Prime & get Access to all 200+ courses offered by PrepInsta in One Subscription

Get over 200+ course One Subscription

Courses like AI/ML, Cloud Computing, Ethical Hacking, C, C++, Java, Python, DSA (All Languages), Competitive Coding (All Languages), TCS, Infosys, Wipro, Amazon, DBMS, SQL and others

Java Program to Convert the LinkedList into an Array and vice versa

What is LinkedList ?

Algorithm to Convert the LinkedList into an Array:

Pseudo Code:

Example:

Algorithm to Convert the Array into an LinkedList:

Pseudo Code:

Example:

Prime Course Trailer

Related Banners

Get over 200+ course One Subscription

Checkout list of all the video courses in PrepInsta Prime Subscription

Checkout list of all the video courses in PrepInsta Prime Subscription