Linked List java

import java.io.*;
import java.util.Scanner;
/**
 * Created by MOHIT on 25-07-2016.
 */
class ListElement{

    public int data;
    public ListElement link;
    public ListElement list1,list2;

    Scanner sc = new Scanner(System.in);
    //construtor
    ListElement(int data){
        this.data = data;
        this.link = null;
    }

    //method to update data in List element
    void updatedata(int data){
        this.data = data;
    }

    //method to setup the Link
    void setLink(ListElement node){
        this.link = node;
    }

    int getdata(){
        return this.data;
    }

    ListElement getNextNode(){
        return this.link;
    }

    //method that returns length of list
    int length(){
        ListElement node = this;
        int length_of_list = 1;

        if(node == null){
            return 0;
        }

        while(node.link != null){
            length_of_list++;
            node = node.getNextNode();
        }

        return length_of_list;
    }

    ListElement insert(ListElement head,ListElement node,int position){

        ListElement previousNode = new ListElement(head.data);
        previousNode.setLink(head.link);

        if(head == null){
            return node;
        }
        else{
            int size = length();
            if(position > size+1){
                System.out.println("Invalid position.");
                System.out.println("Valid positions are from 0 to " + size);
                return head;
            }
            if(position == 1){
                node.setLink(head);
                return node;
            }
            else if(position == 2){
                ListElement temp = new ListElement(-11);
                temp.setLink(head.link);
                head.setLink(node);
                node.setLink(temp.getNextNode());
            }
            else{
                int pos = 1;
                while(pos != position-1){
                    previousNode = previousNode.getNextNode();
                    pos++;
                }
                //ListElement temp = head.getNextNode();

                previousNode.setLink(node);
                node.setLink(null);
            }
        }
        return head;
    }

    ListElement insertAtEnd(ListElement node){
        ListElement head = this;
        int size = head.length();

        ListElement temp = this;
        while(temp.link!=null){
            temp = temp.getNextNode();
        }
        temp.setLink(node);
        return head;
    }

    ListElement deleteByPosition(ListElement head ,int position){
        ListElement previousNode = head;

        if(position == 1){
            head = head.getNextNode();
            return head;
        }
        else{
            int pos = 1;
            while(pos != position-1){
                previousNode = previousNode.getNextNode();
                pos++;
            }
            ListElement currentNode = previousNode.getNextNode();
            previousNode.setLink(currentNode.getNextNode());
            currentNode.setLink(null);
            currentNode = null;
        }

        return head;
    }

    ListElement deleteByData(ListElement head , int data){
        ListElement previousNode = head;
        ListElement currentNode = head;
        if(data == currentNode.data){
            head.setLink(currentNode.getNextNode());

        }
        else{
            while(data != currentNode.data){
                previousNode = currentNode;
                currentNode = currentNode.getNextNode();
            }
            previousNode.setLink(currentNode.getNextNode());
            currentNode.setLink(null);
            currentNode = null;
        }
        return head;
    }

    void display(ListElement head){
        ListElement node = head;
        int position = 1;
        while(node!= null){
            System.out.println("Position " + position + " = " + node.data);
            position++;
            node = node.getNextNode();
        }
    }

    ListElement reverse(){
        ListElement head = this;
        int size = head.length();
        int[] stack = new int[size];
        int i=0;
        ListElement temp = this;
        while(temp.link != null){
            stack[i] = temp.data;
            i++;
            temp = temp.getNextNode();
        }
        stack[i] = temp.data;

        int pos = 2;
        ListElement start = new ListElement(stack[i]);
        for(int j=size-1 ; j>0 ; j--){
            ListElement node = new ListElement(j);
            insert(start,node,pos);
            pos++;
        }
        return start;
    }

    int findElement(int data){
        ListElement node = new ListElement(this.data);
        node.setLink(this.link);
        boolean isPresent = false;
        int position = 1;
        while(!isPresent){
            if(node.data == data){
                isPresent = true;
            }
            else{
                if(node.getNextNode()!= null){
                    node = node.getNextNode();
                    position++;
                }
                else{
                    break;
                }
            }
        }

        if(isPresent){
            return position;
        }
        else{
            return -1;
        }
    }

    int getElement(int position){
        ListElement node = new ListElement(this.data);
        node.setLink(this.link);

        int size = this.length();
        if(size < position){
            return -1111;
        }
        else {
            int pos = 1;
            while (pos != position) {
                node = node.getNextNode();
                pos++;
            }
            return node.data;
        }
    }

    int[] convertToArray(){
        ListElement head = this;
        int size = head.length();
        int[] list = new int[size];
        int position = 0;
        while(head.link != null){
            list[position] = head.data;
            position++;
            head = head.getNextNode();
        }
        list[position] = head.data;

        return list;
    }

    int findMax(){
        ListElement node = new ListElement(this.data);
        node.setLink(this.link);

        int max = 0;
        while(true){

            if(max < node.data){
                max = node.data;
            }
            if(node.getNextNode()!= null){
                node = node.getNextNode();
            }
            else{
                break;
            }
        }
        return max;
    }

    int findMin(){
        ListElement node = new ListElement(this.data);
        node.setLink(this.link);

        int min = node.data;
        while(true){

            if(min > node.data){
                min = node.data;
            }
            if(node.getNextNode()!= null){
                node = node.getNextNode();
            }
            else{
                break;
            }
        }
        return min;
    }

    ListElement makeDummyList() {
        ListElement head = this;
        for(int i=2 ; i < 10 ; i++){
            ListElement node = new ListElement(i);
            head.insert(head,node,i);
        }
        return head;
    }

    int countOccurences(int data) {
        int count = 0;
        ListElement head = this;
        while(head.link != null){
            if(head.data == data){
                count++;
            }
            head = head.getNextNode();
        }
        if(head.data == data){
            count++;
        }
        return count;
    }

    ListElement pop(){
        ListElement head = this;
        if(head.link == null){
            return null;
        }
        else{
            head = head.getNextNode();
            return head;
        }
    }

    ListElement recursiveReverse(ListElement previousNode){
        /*ListElement currentNode = this;
        if(currentNode.link != null){
            previousNode = currentNode;
            currentNode.link.recursiveReverse(previousNode,head);
        }
        if(previousNode != null){
            currentNode.link = previousNode;
            previousNode.link = null;
        }*/
        return this;
    }

}
public class LinkedList {



    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        ListElement head = new ListElement(1);
        head.setLink(null);
        int cont =1;
        head = head.makeDummyList();
        while(cont == 1){
            System.out.println("Program to implement linked list");
            System.out.println("The Following choices are availiable : ");
            System.out.println("1.Insert element in Linked List");
            System.out.println("2.Delete element from Linked List");
            System.out.println("3.Display Linked List");
            System.out.println("4.Display Length of Linked List");
            System.out.println("5.Find element in Linked List");
            System.out.println("6.Get data from a position in Linked List");
            System.out.println("7.find Max and Min from Linked List");
            System.out.println("8.Reverse Linked List");
            System.out.println("9.Convert Linked List to Array");
            System.out.println("10.Insert element at the end");
            System.out.println("11.Count Occurences of an element");
            System.out.println("12.Pop Element from Linked List");
            System.out.println("13.FrontBack Split Linked List");
            System.out.println("0.Exit");
            System.out.print("Enter Your choice :");

            int choice = sc.nextInt();

            switch(choice){

                case 1:
                    System.out.print("Enter data : ");
                    int data = sc.nextInt();
                    System.out.print("Enter position : ");
                    int position = sc.nextInt();

                    ListElement node = new ListElement(data);
                    if(head == null){
                        head = node;
                    }
                    else{
                        int length = head.length();
                        head = head.insert(head,node,position);
                    }
                    break;

                case 2:
                    System.out.println("There are two choices :");
                    System.out.println("1.Delete by data");
                    System.out.println("2.Delete by position");
                    System.out.print("Enter Your choice :");
                    int choices = sc.nextInt();
                    switch (choices){
                        case 1:
                            System.out.print("Enter the data to be deleted : ");
                            int deleteData = sc.nextInt();
                            head = head.deleteByData(head,deleteData);
                            break;

                        case 2:
                            System.out.print("Enter position of element to be deleted : ");
                            int pos = sc.nextInt();
                            head = head.deleteByPosition(head, pos);
                            break;
                    }
                    break;

                case 3:
                    head.display(head);
                    break;

                case 4:
                    if(head == null){
                        System.out.println("The Length of Linked List is 0");
                    }
                    else{
                        int length = head.length();
                        System.out.println("The Length of Linked List is " + length);
                    }

                    break;

                case 5:
                    System.out.print("Enter the element to be searched : ");
                    int element = sc.nextInt();
                    int pos = head.findElement(element);
                    if(pos == -1){
                        System.out.println("The entered element is not present in the list");
                    }
                    else{
                        System.out.println("The Entered element is found at position " + pos );
                    }
                    break;

                case 6:
                    System.out.print("Enter the position : ");
                    position = sc.nextInt();
                    int ele = head.getElement(position);
                    if(ele == -1111){
                        System.out.println("Invalid position number");
                    }
                    else{
                        System.out.println("The data at position " + position + " is " + ele );
                    }
                    break;

                case 7:
                    int max = head.findMax();
                    int min = head.findMin();

                    System.out.println("The Max element is : " + max);
                    System.out.println("The Min element is : " + min);
                    break;

                case 8:
                    ListElement rev = null;
                    rev = head.reverse();
                    rev.display(rev);
                    break;

                case 9:
                    int[] list = head.convertToArray();
                    int length = list.length;
                    for(int i=0 ; i<length ; i++){
                        System.out.println("Position " + i + " = " + list[i]);
                    }
                    break;

                case 10:
                    System.out.print("Enter data : ");
                    data = sc.nextInt();
                    node = new ListElement(data);
                    head.insertAtEnd(node);
                    break;

                case 11:
                    System.out.print("Enter data : ");
                    data = sc.nextInt();
                    int count = head.countOccurences(data);
                    System.out.println("The element " + data + " was found " + count + " times in the Linked list");
                    break;

                case 12:
                    head = head.pop();
                    head.display(head);
                    break;

                case 0:
                        cont = 0;
                        break;

            }
        }
    }

}