STACK JAVA

Develop a stack class to hold a maximum of 10 integers with suitable methods. Develop a JAVA main method to illustrate Stack operations

PROGRAM:

package jo;

import java.util.*;

 

public class Stack {

    int top; // define top of stack

    int maxsize = 10; // max size of the stack

    int[] stack_arry = new int[maxsize]; // define array that will hold stack elements

 

    Stack() {

        top = -1;

    }

 

    boolean isEmpty() {

        return (top < 0);

    }

 

    boolean push(int val) {

        if (top == maxsize - 1) {

            System.out.println("Stack Overflow !!");

            return false;

        } else {

            top++;

            stack_arry[top] = val;

            return true;

        }

    }

 

    boolean pop() {

        if (top == -1) {

            System.out.println("Stack Underflow !!");

            return false;

        } else {

            System.out.println("Item popped: " + stack_arry[top--]);

            return true;

        }

    }

 

    void display() {

        System.out.println("Printing stack elements..... ");

        for (int i = top; i >= 0; i--) {

            System.out.println(stack_arry[i]);

        }

    }

 

    // ✅ main method

    public static void main(String[] args) {

        Stack stck = new Stack();

        stck.push(10);

        stck.push(20);

        stck.push(30);

        stck.push(40);

 

        System.out.println("\nAfter Push Operation...");

        stck.display();

 

        stck.pop();

        stck.pop();

 

        System.out.println("\nAfter Pop Operation...");

        stck.display();

    }

}

 

}

viva questions

1) What is Constructor?
A constructor in Java is a special method that is automatically called when an object is created.

• Its name is the same as the class name.
• It has no return type (not even void).
• It is used to initialize object variables.

Example:

class Demo {

    int x;

    Demo() { // constructor

        x = 10;

    }

}

2) What is Stack?
A stack is a linear data structure that follows the LIFO principle — Last In, First Out.

• The last element inserted is the first one removed.
• Think of it like a stack of plates — you put on top, and take from the top.

3) What are all the operations performed on a stack?
Common stack operations are:

• push(x) → Add an element on top of the stack.
• pop() → Remove the top element from the stack.
• peek() / top() → View the top element without removing it.
• isEmpty() → Check if the stack is empty.
• (Sometimes) isFull() → Check if the stack is full (for fixed-size stacks).

4) What is the role of top in a stack?

• top is an index (pointer) that keeps track of the position of the last inserted element in the stack.
• Initially, top = -1 (stack is empty).
• When we push, top is incremented.
• When we pop, top is decremented.
• It helps in knowing where the next element should be inserted or removed.