Top 5 Stack Interview Questions in Java

Exercise 1: Implementing a Basic Stack

Objective: Implement a basic stack with push, pop, and peek methods.

public class BasicStack {
    private Node top;

    public BasicStack() {
        this.top = null;
    }

    public void push(int data) {
        Node node = new Node(data);
        node.next = top;
        top = node;
    }

    public int pop() {
        if (top == null) throw new IllegalStateException("Stack is empty");
        int data = top.data;
        top = top.next;
        return data;
    }

    public int peek() {
        if (top == null) throw new IllegalStateException("Stack is empty");
        return top.data;
    }

    private static class Node {
        int data;
        Node next;

        Node(int data) {
            this.data = data;
        }
    }
}

Exercise 2: Checking Balanced Parentheses

Objective: Write a method to determine if a string of parentheses is balanced using a stack.

public boolean isBalanced(String s) {
    Stack<Character> stack = new Stack<>();

    for (char c : s.toCharArray()) {
        if (c == '(') {
            stack.push(c);
        } else if (c == ')') {
            if (stack.isEmpty()) {
                return false;
            }
            stack.pop();
        }…