Java Full Stack with React Interview Questions in Chandigarh

@SpringBootApplication @EnableScheduling public class App { } @Component public class CleanupJob { private final SessionRepository repo; public CleanupJob(SessionRepository repo) { this.repo = repo; } @Scheduled(cron = "0 0 2 * * *", zone = "Asia/Kolkata") public void removeExpiredSessions() { repo.deleteByExpiresAtBefore(Instant.now()); } } // With several instances, use ShedLock so only one runs the job.

SELECT order_date, SUM(amount) AS daily_sales, SUM(SUM(amount)) OVER ( ORDER BY order_date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW ) AS running_total FROM orders WHERE order_date >= DATE '2026-10-01' AND order_date < DATE '2026-11-01' GROUP BY order_date ORDER BY order_date;

String text = "java is fun and java is fast"; Map<String, Long> freq = Arrays.stream(text.toLowerCase().split("\\s+")) .collect(Collectors.groupingBy( Function.identity(), LinkedHashMap::new, Collectors.counting())); System.out.println(freq); // {java=2, is=2, fun=1, and=1, fast=1}

function debounce(fn, delay = 300) { let timer; return function (...args) { clearTimeout(timer); timer = setTimeout(() => fn.apply(this, args), delay); }; } const search = debounce(term => { fetch(`/api/products?q=${encodeURIComponent(term)}`); }, 400); input.addEventListener('input', e => search(e.target.value)); // Only the last call within 400 ms actually runs.

const products = [ { name: 'Pen', price: 20, qty: 10, inStock: true }, { name: 'Bag', price: 900, qty: 0, inStock: false }, { name: 'Book', price: 250, qty: 4, inStock: true }, ]; const total = products .filter(p => p.inStock) .map(p => p.price * p.qty) .reduce((sum, value) => sum + value, 0); console.log(total); // 1200

SELECT e.name AS employee, e.salary, m.name AS manager, m.salary AS manager_salary FROM employees e JOIN employees m ON e.manager_id = m.id WHERE e.salary > m.salary; -- A self join treats the same table as two roles.

@Entity @Table(name = "products") public class Product { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(nullable = false, length = 120) private String name; @Column(nullable = false, precision = 10, scale = 2) private BigDecimal price; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "category_id") private Category category; protected Product() {} // required by JPA }

function cartReducer(state, action) { switch (action.type) { case 'add': return { count: state.count + 1 }; case 'remove': return { count: Math.max(0, state.count - 1) }; case 'reset': return { count: 0 }; default: throw new Error('Unknown action ' + action.type); } } function Cart() { const [state, dispatch] = useReducer(cartReducer, { count: 0 }); return ( <div> <span>Items: {state.count}</span> <button onClick={() => dispatch({ type: 'add' })}>+</button> <button onClick={() => dispatch({ type: 'remove' })}>-</button> </div> ); }

# application.yml app: payment: timeout-ms: 3000 retry-count: 2 @ConfigurationProperties(prefix = "app.payment") @Validated public record PaymentProperties( @Min(500) int timeoutMs, @Max(5) int retryCount) {} @SpringBootApplication @EnableConfigurationProperties(PaymentProperties.class) public class App { } // Relaxed binding maps timeout-ms to timeoutMs automatically.

-- Find duplicates SELECT email, COUNT(*) AS cnt FROM users GROUP BY email HAVING COUNT(*) > 1; -- Keep the lowest id, delete the rest (MySQL / PostgreSQL) DELETE FROM users u USING users k WHERE u.email = k.email AND u.id > k.id; -- PostgreSQL syntax -- Then add: ALTER TABLE users ADD CONSTRAINT ux_email UNIQUE (email);