SingleLinkedList.java

import java.util.Scanner;

//Node class

class Node{
    int data;
    Node next;
}

//Main Class

class Main{
    static Node head;

    //Function to add First element when there is no element in Linked List

    static void firstElement(int data){
        System.out.println("It is the first element of the linked list");
        head = new Node();
        head.data = data;
        head.next = null;
    }

    // Function to add element at last

    static void addLast(int data){
        if(head==null){
            firstElement(data);
            return;
        }
        Node newNode = new Node();
        Node temp = head;
        newNode.data = data;
        newNode.next = null;
        while(temp.next!=null){
            temp = temp.next;
        }
        temp.next = newNode;
        System.out.println("Data added to last successfully");
    }

    //Function to add element at starting

    static void addFirst(int data){
        Node newNode = new Node();
        newNode.data = data;
        if(head==null){
            firstElement(data);
            return;
        }else{
            newNode.next = head;
            head = newNode;
        }
        System.out.println("Data added successfully at first");
    }

    //Function to delete the element

    static void delete(int data){
        Node temp = head;
        if(temp.data == data){
            head = head.next;
        }
        while(temp.next!=null){
            if(temp.next.data==data){
                temp.next = temp.next.next;
                System.out.println("Deleted data "+data+" successfully");
                return;
            }
            temp = temp.next;
        }
        System.out.println(data + " not found in the linked list");
    }

    //Function to Search the element

    static void search(int data){
        Node temp = head;
        while(temp!=null){
            if(temp.data==data){
                System.out.println("Data Found");
                return;
            }
            temp = temp.next;
        }
        System.out.println("Data not found");
    }

    //Function to print the Data in the Linked List

    static void print(){
        Node temp = head;
        if(temp==null){
            System.out.println("No data in the linked list");
            return;
        }
        System.out.println("Data stored in linked list are:");
        while(temp!=null){
            System.out.println(temp.data);
            temp = temp.next;
        }
    }

    //Function to find and print the middle element in the linked list

    static void findMiddleElement(){
        Node n1 = head,n2 = head;
        if(head==null) {
            System.out.println("No data found");
            return;
        }
        boolean even = false;
        while(n1.next!=null&&n2.next!=null){
            n2 = n2.next;
            if(n2.next!=null)
                n2 = n2.next;
            else {
                System.out.print("There are two middle elements : " + n1.data + " and ");
                even = true;
            }
            n1 = n1.next;
        }
        if(even)
            System.out.println(n1.data);
        else
            System.out.println("Middle element = "+n1.data);
    }

    //Main Function

    public static void main(String args[]){
        Scanner scan = new Scanner(System.in);
        while(true){
            System.out.println("Enter the command:\t1 - print\t2 - addFirst\t3 - addLast\t4 - delete\t5 - Search\t6 - Middle\t7 - Exit");
            int n = scan.nextInt();
            switch (n){
                case 1:
                    print();
                    break;
                case 2:
                    int d = scan.nextInt();
                    addFirst(d);
                    break;
                case 3:
                    d = scan.nextInt();
                    addLast(d);
                    break;
                case 4:
                    d = scan.nextInt();
                    delete(d);
                    break;
                case 5:
                    d = scan.nextInt();
                    search(d);
                    break;
                case 6:
                    findMiddleElement();
                    break;
                case 7:
                    scan.close();
                    return;
                default:
                    System.out.println("Type a valid command");
            }
            System.out.println("--------------------------------");
        }
    }
}