Saquib Aftab ✓

[image] Embedded Servers in Spring Boot ✅ In older Java web apps, we usually build a WAR file and deploy it to an external server, such as a standalone Tomcat or JBoss. With Spring Boot, the server is embedded inside the application. The server libraries are bundled in the classpath

[image] Interview Question: Explain the internal working of HashMap? How does it handle collisions?

[image] Important Java Library #1: Apache Commons Lang 👉 ✅This library provides small helper utilities like StringUtils, ObjectUtils, and EqualsBuilder, which can save time and produce clean code.

[image] What causes a java.lang.OutOfMemoryError in Java?

[image] Java Interviewer: How do you create and start threads in Java? Answer: ✅There are three common approaches: - Extending Thread - Implementing Runnable - Using executors (including virtual thread executors)

[image] Understanding JVM Memory Areas ✅

[image] Spring Security Concepts: OAuth2 Resource Server ✅ With a single OAuth2ResourceServer declaration, Spring Security will: 1. Extract the Authorization: Bearer <token> header from every request 2. Validate the token’s signature against your Authorization Server’s public key

[image] ➡️Pagination is the technique which divides large datasets into smaller, manageable chunks. These chunks are called pages. Instead of fetching and displaying all data at once, we retrieve and show only the data a user needs right now. ✅ What are the benefits of pagination?

[image] ✅Garbage Collector in Java: Java gives us multiple GC options. Picking the right one depends on your latency and throughput requirements.

[image] Interview Questions on Java Concurrency ✅ ➡️ What is the real difference between volatile, synchronized, and atomic classes? ➡️ When would one be enough and when would you need the others? ➡️ How do visibility, atomicity, and ordering matter in multithreaded code?

[image] Factory vs Abstract Factory Design Pattern ✅️

[text] If I had to learn Spring Boot from zero today, this is the order I'd follow: 1. Core Java first. Collections, streams, exceptions. 2. Basics of HTTP. Methods, status codes, headers. 3. One simple REST API. Just CRUD. 4. A real database. PostgreSQL, not only H2. 5. Spring Data

[image] JPA (now called Jakarta Persistence) is a specification. It defines a set of standard APIs and annotations for object‑relational mapping in Java. Hibernate ORM is a popular implementation of that specification. It takes the JPA rules and provides a working library that you add

[text] Java tip: isEmpty() checks if a string has length 0. isBlank() also treats spaces-only strings as empty. Use isBlank() for user input.

[text] Java Records replace 30 lines of boilerplate with one: record User(String name, int age) {} Constructor, getters, equals, hashCode, toString. All done.

[text] Java 25 lets you write a full program like this: void main() { IO.println("Hello"); } No class. No public static. No String[] args. Really nice for beginners and small scripts. For real projects you'll still write classes, and that's fine.