hijaz dkk linkedlist

import java.util.Scanner;
class Node{
    protected int data;
    protected Node link;
    public Node(){
        link = null;
        data = 0;
    }
    public Node (int d,Node n){
        data = d;
        link = n;
    }
    public void setLink(Node n){
        link = n;
    }
    public void setData(int d){
        data = d;
    }
    public Node getLink(){
        return link;
    }
    public int getData(){
        return data;
    }
}
class linkedList{
    protected Node start;
    protected Node end;
    public int size;
    public linkedList(){
        start = null;
        end = null;
        size = 0;
    }
    public boolean isEmpty(){
        return start == null;
    }
    public int getSize(){
        return size;
    }
    public void insertAtStart(int val){
        Node nptr = new Node(val, null);size++;
        if (start == null){
            start = nptr;
            end =start;
        }
        else{
            nptr.setLink(start);
            start = nptr;
        }
    }
    public void insertAtEnd(int val){
        Node nptr = new Node(val,null);size++;
        if (start == null){
            start = nptr;
            end = start;
        }
        else{
            end.setLink(nptr);
            end = nptr;
        }
    }
    public void insertAtPos(int val,int pos){
        Node nptr = new Node(val,null);
        Node ptr = start;
        pos = pos-1;
        for (int i=1;i<size;i++){
            if (i == pos){
                Node tmp = ptr.getLink();
                ptr.setLink(nptr);
                nptr.setLink(tmp);break;
            }
            ptr = ptr.getLink();
        }size++;
    }
    public void deleteAtPos(int pos){
        if(pos == 1){
            start = start.getLink();size++;
            return;
        }
        if (pos == size){
            Node s = start;
            Node t = start;
            while (s != end){
                t = s;
                s = s.getLink();
            }
            end = t;
            end.setLink(null);size++;
            return;
        }
        Node ptr = start;
        pos = pos-1;
        for (int i=1;i<size-1;i++){
            if (i == pos){
                Node tmp = ptr.getLink();
                tmp = tmp.getLink();
                ptr.setLink(tmp);break;
            }
            ptr = ptr.getLink();
        }size++;
    }
    public void display(){
        System.out.print("\n Singly Linked List = ");
        if (size == 0){
            System.out.print("\n Empty = ");return;
        }
        if (start.getLink() == null){
            System.out.println(start.getData());return;
        }
        Node ptr = start;
        System.out.print(start.getData()+"->");
        ptr = start.getLink();
        while (ptr.getLink() != null){
            System.out.print(ptr.getData()+"->");
            ptr = ptr.getLink();
        }
        System.out.print(ptr.getData()+" \n");
    }
}
public class PrakSDA {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        linkedList  list= new linkedList();
        System.out.println("Linked List max 5 :");char ch;
        do{
            System.out.println("\n Singly Linked List Opration ");
            System.out.println("1. Masukan Diawal");
            System.out.println("2. Masukan Diakhir");
            System.out.println("3. Masukan Pada Posisi");
            System.out.println("4. Hapus Pada Posisi");
            System.out.println("5. Cek Kosong");
            System.out.println("6. get size");
            System.out.println("");
            System.out.print("Masukan Perintah : ");
            int choice=in.nextInt();
            switch (choice){
                case 1 :
                    System.out.println("Masukan Elemen Data");
                    list.insertAtStart(in.nextInt());break;
                case 2 :
                    System.out.println("Masukan Elemen Data");
                    list.insertAtEnd(in.nextInt());break;
                case 3 :
                    System.out.println("Masukan Elemen Data");
                    int num = in.nextInt();
                    System.out.println("Masukan Posisi : ");
                    int pos = in.nextInt();
                    if (pos <= 1 || pos > list.getSize())
                        System.out.println("Posisi tidak valid !!!");
                    else
                        list.insertAtPos(num, pos);break;
                case 4 :
                    System.out.println("Masukan Posisi");
                    int p = in.nextInt();
                    if (p < 1 || p > list.getSize())
                        System.out.println("Posisi tidak valid !!!");
                    else
                        list.deleteAtPos(p);break;
                case 5 :
                    System.out.println("Status Kosong ="+list.isEmpty());break;
                case 6 :
                System.out.println("Size = "+ list.getSize() +" \n");
                break;
                default :
                    System.out.println("Input Salah !!!");break;
            }
            list.display();
            System.out.println("Lanjutkan ? (Ketik Y Atau N)");
            ch = in.next().charAt(0);
        }while (ch == 'Y' || ch == 'y');

    }
}