Java Program for Stack Simulation

Program

import java.io.*;
import java.util.*;
public class stack {
    private final int size = 10;
    private int top;
    private int st[];
    stack() {
        top = -1;
        st = new int[size];
    }
    void push(int item) {
        if (top == st.length - 1) {
            System.out.println("Stack overflow");
            return;
        } else {
            st[++top] = item;
            System.out.println("Element pushed is:\t" + st[top]);
            return;
        }
    }
    void pop() {
        if (top == -1) {
            System.out.println("Stack underflow");
            return;
        } else {
            System.out.println("Element poped is:\t" + st[top--]);
            return;
        }
    }
    void display() {
        if (top == -1) {
            System.out.println("Stack underflow");
            return;
        } else {
            System.out.println("Contents of stack:");
            for (int i = 0; i <= top; i++)
                System.out.println(st[i]);
            return;
        }
    }
}
public class StackSimulation {
    public static void main(String[] args) {
        stack s = new stack();
        int choice;
        Scanner sc = new Scanner(System.in);
        System.out.println("STACK");
        while (true) {
            System.out.println("1. Push\n2. Pop\n3. Display\n4. Exit");
            System.out.println("Enter choice");
            choice = sc.nextInt();
            switch (choice) {
            case 1:
                System.out.println("Enter the item to push");
                int item = sc.nextInt();
                s.push(item);
                break;
            case 2:
                s.pop();
                break;
            case 3:
                s.display();
                break;
            case 4:
                sc.close();
                System.exit(0);
                break;
            default:
                System.out.println("Invalid choice");
            }
        }
    }
}

This program demonstrates stack simulation in Java using an array-based implementation. The stack operates on the LIFO (Last In, First Out) principle, supporting operations like push, pop, and display.

Key Concepts of the Stack:

1. Push: Add an element to the top of the stack.
2. Pop: Remove the topmost element from the stack.
3. Display: Show all elements currently in the stack.
4. Overflow and Underflow:
   • Overflow occurs when trying to push an element into a full stack.
   • Underflow occurs when trying to pop an element from an empty stack.

1. Class stack:

• Implements the stack functionality.
• Data Members:
  • size: Maximum capacity of the stack (set to 10).
  • top: Tracks the index of the topmost element (initialized to -1).
  • st[]: Array to hold stack elements (size is 10). The stack is implemented using a fixed-size array (st[]), with top tracking the index of the top element.
• Methods:
  1. Constructor (stack()):
     • Initializes top to -1 and creates the stack array with a fixed size (size).
  2. push(int item):
     • Adds a new element to the stack if it is not full.
     • If the stack is full (top == st.length - 1), prints "Stack overflow".
  3. pop():
     • Removes and returns the topmost element if the stack is not empty.
     • If the stack is empty (top == -1), prints "Stack underflow".
  4. display():
     • Displays all elements from the bottom to the top of the stack.
     • If the stack is empty, prints "Stack underflow".

2. Class StackSimulation:

• Contains the main() method to simulate stack operations.
• Steps:
  1. Creates an object of the stack class.
  2. Uses a while loop to present a menu of stack operations:
     • Push: Add an element to the stack.
     • Pop: Remove the top element from the stack.
     • Display: Show the contents of the stack.
     • Exit: Exit the program.
  3. Based on the user's choice, the program calls the appropriate method of the stack class.

Output

STACK
1. Push
2. Pop
3. Display
4. Exit
Enter choice
2
Stack underflow
1. Push
2. Pop
3. Display
4. Exit
Enter choice
1
Enter the item to push
10
Element pushed is:      10
1. Push
2. Pop
3. Display
4. Exit
Enter choice
1
Enter the item to push
20
Element pushed is:      20
1. Push
2. Pop
3. Display
4. Exit
Enter choice
1
Enter the item to push
30
Element pushed is:      30
1. Push
2. Pop
3. Display
4. Exit
Enter choice
3
Contents of stack:
10
20
30
1. Push
2. Pop
3. Display
4. Exit
Enter choice
4