/*Week 5 :a) Write a Java program that:i) Implements stack ADT*/

/*Week 5 :a) Write a Java program that:i) Implements stack ADT*/

import java.lang.*;

import java.io.*;

import java.util.*;

interface MyInterface {

        int n = 20;

        public void pop();

        public void push();

        public void peek();

        public void display();

}

class StackImplementation implements MyInterface {

        int arr[] = new int[n];

        int top = -1;

        public void push() {

                try {

                        DataInputStream dis = new DataInputStream(System.in);

                        System.out.println("Enter Element");

                        int ele = Integer.parseInt(dis.readLine());

                        arr[++top] = ele;

                } catch (Exception e) {

                        System.out.println("e");

                }

        }

        public void pop() {

                int popper = arr[top];

                top--;

                System.out.println("popped element " + popper);

        }

        public void peek() {

                int popper = arr[top];

                System.out.println("popped element " + popper);

        }

        public void display() {

                if (top < 0) {

                        System.out.println("Stack is empty");

                        return;

                } else {

                        String str = " ";

                        for (int i = 0; i <= top; i++)

                                str = str + " " + arr[i];

                        System.out.println("Elements are " + str);

                }

        }

}

class StackADT {

        public static void main(String arg[]) throws IOException {

                DataInputStream dis = new DataInputStream(System.in);

                StackImplementation stk = new StackImplementation();

                int menu = 0;

                do {

                        System.out.println("1.push \n2.pop \n3.peek \n4.display \n5.Exit");

                        System.out.println();

                        System.out.print("Enter your choice: ");

                        menu = Integer.parseInt(dis.readLine());

                        switch (menu) {

                        case 1:

                                stk.push();

                                break;

                        case 2:

                                stk.pop();

                                break;

                        case 3:

                                stk.peek();

                                break;

                        case 4:

                                stk.display();

                                break;

                        case 5:

                                System.exit(0);

                        }

                } while (menu <= 5);

                System.out.println();

        }

}