Question

Write Java code (do not use Java libraries) to perform the following on a linked list of integers: prepend a new value

Answer 1

If you have any problem with the code feel free to comment.

Program

/*LinkedList implementation*/

class LinkedList {
   Node head;

   //node class for holding data and the next node address
   static class Node {
       int data;
       Node next;

       Node(int data) {
           this.data = data;
       }
   }

   //inserting data to the list
   public void insert(LinkedList list, int data) {
       Node newNode = new Node(data);

       newNode.next = null;

       if (list.head == null)
           list.head = newNode;
       else {

           Node last = list.head;
           // traversing the list to find the last node
           while (last.next != null) {
               last = last.next;
           }
           // putting the value after the last node
           last.next = newNode;
       }
   }

   // insert values at the start of the list
   public void prepend(LinkedList list, int data) {
       Node newNode = new Node(data);

       newNode.next = list.head;

       list.head = newNode;
   }

   // delete value from index
   public void delete(LinkedList list, int index) {
       if (index == 0)
           list.head = list.head.next;
       else {
           Node node = list.head;
           Node temp = null;

           for (int i = 0; i < index - 1; i++) {
               node = node.next;
           }
           temp = node.next;
           node.next = temp.next;
       }
   }

   //printing the values of the list
   public static void printList(LinkedList list) {
       Node currentNode = list.head;
       while (currentNode != null) {
           System.out.print(currentNode.data + " ");
           currentNode = currentNode.next;
       }
       System.out.println();
   }
}

public class Test {//for testing the linked list
   public static void main(String[] args) {
       LinkedList list = new LinkedList();
      
       //inserting values to the linkedlist
       list.insert(list, 1);
       list.insert(list, 2);
       list.insert(list, 3);
      
       System.out.print("LinkedList after insert: ");
       LinkedList.printList(list);
      
       //deleteing value from the list
       list.delete(list, 2);
      
       System.out.print("LinkedList after delete: ");
       LinkedList.printList(list);
      
       //prepending value to the list
       list.prepend(list, 10);
      
       System.out.print("LinkedList after prepend: ");
       LinkedList.printList(list);
   }
}

Output