Implementation of linked list in Java

LinkedList.java

import java.util.Scanner;
class LinkedList {
    static class Node {
        String data;
        int index;
        Node next;
    }
    private static Node head = null;
    public static void main(String[] args) {
        int command = 0;
        System.out.println("Enter your choice:\n" +
                "1 -> Prepend\n" +
                "2 -> Append\n" +
                "3 -> Insert At\n" +
                "4 -> Print List\n" +
                "5 -> Print Item\n" +
                "6 -> Delete Item");
        while(command != -1) {
            Scanner sc = new Scanner(System.in);
            command = sc.nextInt();
            switch (command) {
                case 1:
                    prepend();
                    break;
                case 2:
                    append();
                    break;
                case 3:
                    insertAt();
                case 4:
                    printList();
                    break;
                case 5:
                    printItem();
                    break;
                case 6:
                    deleteNode();
                    break;
                default:
                    command = -1;
                    System.out.println("Invalid input! Program exited.");
                    break;
            }
            System.out.println("\nEnter a new choice: ");
        }
    }
    private static void prepend() {
        System.out.println("Enter the String to be prepended: ");
        Scanner sc = new Scanner(System.in);
        String newString = sc.nextLine();
        Node newEntry = new Node();
        newEntry.data = newString;
        if(head == null)
            newEntry.index = 0;
        else
            newEntry.index = head.index + 1;
        newEntry.next = head;
        head = newEntry;
        System.out.println(newString + " was successfully added to the list.\n");
    }
    private static void append() {
        System.out.println("Enter the String to be appended: ");
        Scanner sc = new Scanner(System.in);
        String newString = sc.nextLine();
        Node newEntry = new Node();
        newEntry.data = newString;
        newEntry.index = 0;
        if (head == null){
            head = newEntry;
            head.next = null;
        }
        else {
            Node temp = head;
            while (temp != null) {
                if (temp.index == 0) break;
                temp.index++;
                temp = temp.next;
            }
            assert false;
            temp.index++;
            temp.next = newEntry;
            newEntry.next = null;
        }
        System.out.println(newString + " was successfully added to the list.\n");
    }
    private static void insertAt() {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter the data: ");
        String newString = sc.nextLine();
        System.out.println("Enter the index where you want to insert it at: ");
        int index = sc.nextInt();
        Node newEntry = new Node();
        newEntry.data = newString;
        newEntry.index = index;
        if (head != null) {
            Node temp = head;
            while (temp != null) {
                if (temp.index == index) break;
                temp.index++;
                temp = temp.next;
            }
            assert false;
            temp.index++;
            newEntry.next = temp.next;
            temp.next = newEntry;

        }
        else if(index == 0) {
            head = newEntry;
            head.next = null;
        }
        else
            System.out.println("The index " + index + " doesn't exists.");
    }
    private static void deleteNode() {
        System.out.println("Enter the index of the item you want to delete: ");
        Scanner sc = new Scanner(System.in);
        int index = sc.nextInt();
        if (index == 0 && head != null) {
            head = null;
            System.out.println("The data at index " + index + " was deleted.");
        }
        else if (head != null) {
            Node temp = head;
            while (temp != null) {
                if (temp.index == index) break;
                temp.index--;
                temp = temp.next;
            }
            assert false;
            temp.data = temp.next.data;
            temp.next = temp.next.next;
            System.out.println("The data at index " + index + " was deleted.");
        }
        else
            System.out.println("Failed to locate the data at index " + index);
    }
    private static void printItem()
    {
        System.out.println("Enter the index of the item you want to print: ");
        Scanner sc = new Scanner(System.in);
        int index = sc.nextInt();
        int check = 0;
        Node temp = head;
        while (temp != null)
        {
            if (temp.index == index) {
                System.out.print("[" + temp.data + ", " + temp.index + "]\n");
                check = 1;
                break;
            }
            temp = temp.next;
        }
        if (check != 1)
            System.out.println("Failed to locate the data at index " + index);
    }
    private static void printList()
    {
        if (head == null)
            System.out.println("List is empty.");
        else {
            Node temp = head;
            while (temp != null) {
                System.out.print("[" + temp.data + ", " + temp.index + "]\n");
                temp = temp.next;
            }
        }
    }
}