pRG FOR IMPLEMENT STACK WITH ARRAY USING JAVA

import java.io.*;
class Stack
{
    int arr[]=new int[10];
    int len=0;
    Stack()
    {
        for(int i=0;i<10;i++)
            arr[i]=0;
    }
    void push(int a)
    {
        if(len<10)
        {
            arr[len]=a;
            len++;
        }
        else System.out.println("Cannot Input more than 10 Numbers");
    }
    int pop()
    {
        if(len>0)
            return arr[len-1];
        else return -1;
    }
    int popAndTop()
    {
        if(len>0)
            return arr[len--];          
        else return -1;
    }
    void main()throws IOException
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        int ch;
        Stack pile=new Stack();
        do
        {
            System.out.println("\tList\n1.Push\n2.Pop\n3.Pop And Top\n4.Exit");
            ch=Integer.parseInt(br.readLine());
            switch(ch)
            {
                case 1:System.out.println("Enter Element");
                       int n=Integer.parseInt(br.readLine());
                       pile.push(n);
                       break;
                case 2:if(pile.pop()!=-1)
                        System.out.println("\t"+pile.pop());
                       else System.out.println("No Elements to Display");
                       break;
                case 3:if(pile.popAndTop()!=-1)
                        System.out.println("\t"+pile.popAndTop());
                       else System.out.println("No Elements to Display");                      
                       break;
                case 4:System.out.println("Goodbye");break;
                default:System.out.println("Invalid choice");
            }
        }while(ch!=4);
    }
}