"Learn Java Generics and Collections with New Book"

Thrilled to finally share this - my new book on Java Generics and Collections is out! Over the past few months, I’ve been talking about Java fundamentals, the parts many skip while chasing frameworks and tools. This book is built around that belief, that real strength in Java comes from understanding what happens beneath the surface. It dives deep into Generics and Collections, explaining not just how to use them, but how they truly work behind the scenes. Because once you grasp these core concepts, every piece of Java code you write starts making a lot more sense. A heartfelt thank you to Sunil Gupta for being an incredible collaborator throughout this journey, your clarity and inputs shaped this book beautifully. Also, a big thank you to BPB for believing in this idea and helping us bring it to life. We wrote this for every Java developer who wants to move beyond syntax and really understand the foundations that power the language. It’s now available on Amazon, and I can’t wait for you all to read it!

Top 10 Java Internals Every Developer must Know --> 𝟭. 𝗝𝗩𝗠 𝗔𝗿𝗰𝗵𝗶𝘁𝗲𝗰𝘁𝘂𝗿𝗲 The brain of Java. Handles class loading, memory management, and execution via the ClassLoader, Memory Areas (Heap, Stack, Metaspace), and Execution Engine (JIT + Interpreter). 𝟮. 𝗖𝗹𝗮𝘀𝘀 𝗟𝗼𝗮𝗱𝗶𝗻𝗴 & 𝗕𝘆𝘁𝗲𝗰𝗼𝗱𝗲 Turning source code into bytecode magic. Dynamic loading via a delegation model ensures security and modularity. Each class lives in one ClassLoader universe. 𝟯. 𝗚𝗮𝗿𝗯𝗮𝗴𝗲 𝗖𝗼𝗹𝗹𝗲𝗰𝘁𝗶𝗼𝗻 (𝗚𝗖) Memory cleanup with attitude. G1, ZGC, and Shenandoah manage heap generations, compacting memory with minimal pause times — so your app doesn’t stutter mid-run. 𝟰. 𝗝𝘂𝘀𝘁-𝗜𝗻-𝗧𝗶𝗺𝗲 (𝗝𝗜𝗧) 𝗖𝗼𝗺𝗽𝗶𝗹𝗮𝘁𝗶𝗼𝗻 When your code gets smarter at runtime. Hot methods are compiled into native code. JIT performs inlining, escape analysis, and optimization based on profiling data. 𝟱. 𝗝𝗮𝘃𝗮 𝗠𝗲𝗺𝗼𝗿𝘆 𝗠𝗼𝗱𝗲𝗹 (𝗝𝗠𝗠) Defines how threads actually see memory. Guarantees “happens-before” rules. Understands visibility, ordering, and atomicity — essential for writing safe concurrent code. 𝟲. 𝗦𝘆𝗻𝗰𝗵𝗿𝗼𝗻𝗶𝘇𝗮𝘁𝗶𝗼𝗻 & 𝗟𝗼𝗰𝗸𝘀 Inside the synchronized keyword. JVM uses biased, lightweight, and heavyweight locks. Too much contention? JVM dynamically escalates the lock strategy. 𝟳. 𝗖𝗹𝗮𝘀𝘀 𝗗𝗮𝘁𝗮 𝗦𝗵𝗮𝗿𝗶𝗻𝗴 (𝗖𝗗𝗦) & 𝗔𝗢𝗧 Faster startup, smaller footprint. CDS stores preloaded classes in a shared archive; AOT (Ahead-of-Time) compilation skips JIT for faster boot — perfect for microservices. 𝟴. 𝗡𝗮𝘁𝗶𝘃𝗲 𝗜𝗻𝘁𝗲𝗿𝗳𝗮𝗰𝗲 (𝗝𝗡𝗜 & 𝗣𝗮𝗻𝗮𝗺𝗮) When Java shakes hands with C/C++. Bridges Java and native code for performance-critical tasks, while Project Panama makes it safer and faster than legacy JNI. 𝟵. 𝗝𝗩𝗠 𝗧𝘂𝗻𝗶𝗻𝗴 & 𝗠𝗼𝗻𝗶𝘁𝗼𝗿𝗶𝗻𝗴 Keep your JVM happy and your prod stable. Tweak -Xmx, -XX:+UseG1GC, use JFR, JConsole, and VisualVM for insights. Heap dumps tell the story of your runtime. 𝟭𝟬. 𝗥𝗲𝗳𝗹𝗲𝗰𝘁𝗶𝗼𝗻 & 𝗠𝗲𝘁𝗮𝗱𝗮𝘁𝗮 Java looking at itself. Power behind frameworks like Spring and Hibernate. Uses class metadata and dynamic proxies to wire behavior at runtime. #java #javaDeepDive #coreJava #javaInternal #javaInterview #softwareEngineering #javaDeveloper #javaWins #modernJava #java25 #jdk #jre #jdkInternal #javaConcurrency #jvm

💻 Mastering the Core of Java DTOs --> equals(), hashCode(), and compareTo() When building DTO (Data Transfer Object) classes in the data layer, these three methods silently ensure data consistency, uniqueness, and proper sorting. While implementing them, I realized, mastering a few core Java fundamentals makes a huge difference in how our applications behave. The three most important methods and interfaces that truly define object behavior are: 1️⃣ equals(Object obj) 🔸Defines how two objects are considered equal. 🔸Used by collections like Set or Map to prevent duplicates. 🔸Always ensure logical equality, not just reference equality. 2️⃣ hashCode() 🔸Returns a unique hash value used in hashing-based collections (HashMap, HashSet). 🔸If you override equals(), you must override hashCode() to maintain consistency. 3️⃣ compareTo(ClassName other) from Comparable<ClassName> 🔸Provides natural ordering for your objects. 🔸Enables sorting with Collections.sort() and TreeSet. Along with these, implementing these two most important interfaces 4️⃣ Serializable 🔸Makes the DTO transferable across different layers, APIs, or storing session data. Used as converted to a byte stream, allowing easy saving, caching, or sending over a network. Example: [for more refer post image] public class Member implements Serializable { … } 5️⃣ Comparable<T>  🔸Gives our objects a natural ordering for sorting and comparison. Example: [for more refer post image] public class Member implements Comparable<Member> {   public int compareTo(Member other) { … } } These methods and interfaces ensure your objects are: ✅ Comparable (for sorting) ✅ Serializable (for transfer) ✅ Consistent (for hashing and equality) 📸 (Attached: My own Java DTO implementation of equals(), hashCode(), and compareTo() --> written in Vim on Linux 💻) Together, these create the foundation of reliable data-layer design, something that every backend developer must get right. I’m consistently sharpening my core Java skills to get placement for backend and enterprise-level development roles. Because strong fundamentals always make the best developers. Github: https://lnkd.in/deSpAU3K #JavaDeveloper #JavaProject #Java #SoftwareDevelopment #Programming

🔥 Java Revision Day — JVM Architecture Explained 🧩 Today’s Java revision focused on one of the most powerful and core components of Java — the JVM (Java Virtual Machine). It’s fascinating how this single engine makes Java truly platform-independent through the “Write Once, Run Anywhere” concept! ☕ 🧠 What is JVM? The Java Virtual Machine (JVM) is the heart of the Java Runtime Environment (JRE). It executes Java bytecode (.class files) and converts it into machine code for the operating system. ✅ Runs the same Java program across different OS (Windows, Mac, Linux). ✅ Provides automatic memory management and security. ⚙️ JVM Architecture Components 1️⃣ Class Loader Subsystem Responsible for loading class files into memory. It has three main parts: Bootstrap Loader: Loads core Java classes (java.lang, java.util, etc.) Extension Loader: Loads additional extension libraries. Application Loader: Loads user-defined classes from the project. 2️⃣ Runtime Data Areas This is where all the data is stored while the program runs 👇 Method Area: Stores class-level data, static variables, method info. Heap: Contains all Java objects and instance variables (shared among threads). Stack: Stores method calls and local variables (each thread has its own stack). PC Register: Keeps track of the current instruction being executed. Native Method Stack: Handles native (C/C++) methods through JNI. 3️⃣ Execution Engine The brain of the JVM that executes bytecode. Interpreter: Executes bytecode line by line. JIT Compiler (Just-In-Time): Converts frequently used bytecode into native code for better performance. Garbage Collector: Automatically removes unused objects from memory — making Java memory-efficient. 4️⃣ Native Interface & Libraries JNI (Java Native Interface): Allows Java to communicate with native applications (like C/C++). Native Libraries: Provide low-level system functionality. 🗣️ My Reflection Every time I explore Java’s architecture, I’m amazed by how thoughtfully it’s built — a system that blends performance, security, and portability so seamlessly. Learning about the JVM has strengthened my understanding of how Java runs behind the scenes. 💪 #Java #JVM #Programming #Coding #SoftwareDevelopment #FullStackDevelopment #LearningJourney #DailyLearning #RevisionDay #TAPAcademy #TechCommunity #SoftwareEngineering #JavaDeveloper #WriteOnceRunAnywhere #CareerGrowth

Stop Rewriting Code: Java Generics Explained Want to write a single piece of Java code that works perfectly for multiple data types? That's the power of Java Generics. Our blog post breaks down this fundamental concept, showing you how to: ✅ Ensure type safety before runtime. ✅ Significantly reduce boilerplate code. ✅ Build more flexible and elegant libraries. A quick read that delivers lasting coding benefits: https://lnkd.in/dD_pFMy9 #java #generics #javaprogramming #codingtips #reusablecode #softwaredevelopment #developerlife #programmingskills #docsallover 

Java Full Stack Development — Complete Overview A concise mind map illustrating the key components of modern backend development: ☕ Java – OOP Concepts, Collections, Exception Handling 🌿 Spring Boot – REST APIs, JPA/Hibernate, Dependency Injection 🐬 MySQL – Queries, Joins, Relationships, Database Design 🧰 Tools – Maven, Postman, Docker, GitHub This visual represents how each layer connects — from frontend to backend to database, forming a robust and scalable full stack architecture. #Java #SpringBoot #MySQL #FullStackDevelopment #BackendDevelopment #SoftwareEngineering #Programming #SQL #Database #DataEngineering #Coding #Developer #Learning #SQLJoins #FullStack #javacoding #Backend #WebDevelopment #SpringFramework #Database #API #Developers #TechCareer #CodingJourney #LearnToCode

Day 94: Nobody Told Me Java Application Could Start This Fast and The Rabbit hole I explored https://lnkd.in/gbRa8Rx4 Last week, one of my brilliant colleague Tahmid Khan bhai's knowledge-sharing session on Java performance tuning sent me down a rabbit hole. What I discovered completely changed how I think about startup time! Here's what I learned: startup time isn't just "JVM is slow" - it's a combination of classloading, framework initialization, reflection overhead, and I/O operations. Each eats up precious seconds. The Game-Changers I Found: 🔹 AppCDS (Class Data Sharing) - Snapshot loaded classes and reuse them 🔹 Lazy Initialization - Load beans only when needed, not all at startup 🔹 GraalVM Native Image - AOT compilation for millisecond startups 🔹 JLink Custom JRE - Cut your runtime from 300MB → 42MB 🔹 Parallel Initialization - Why initialize sequentially when you have cores? 🔹 Dependency Pruning - Fewer JARs = less scanning From exploration across: ✅ JVM-level optimizations (works for ANY Java app) ✅ Spring Boot-specific techniques ✅ Build & packaging tricks ✅ Architecture patterns ✅ Docker deployment magic The best part? Most of these require ZERO code changes. Just smarter JVM configuration and thoughtful architecture. Big thanks to my colleague for sparking this exploration. Knowledge sharing sessions like these are pure gold! 💡 Your Java app doesn't have to start slow. The tools exist. You just need to know where to look. What's your biggest Java startup pain point? 👇 #Java #PerformanceOptimization #SpringBoot #JVM #100DaysOfJava #GraalVM #TechLearning

⚙️ equals() and hashCode() — The Silent Duo That Holds Java Collections Together 🧠 You use them every day — maybe without realizing it. But these two methods literally decide how your Java objects behave in collections. Let’s decode them 👇 --- 🔹 1️⃣ The Golden Rule If two objects are equal, they must have the same hash code. But having the same hash code ❌ doesn’t mean they’re equal. It’s like house numbers — two houses can’t share one number, but two houses in different cities can both have “21A” 🏠 --- 🔹 2️⃣ How Collections Use Them Take a HashMap or HashSet: When you add an object, Java: 1️⃣ Uses hashCode() to find the right bucket 🪣 2️⃣ Uses equals() to find the exact match inside that bucket If you break the contract (override one but not the other)… 💥 your map can lose entries or fail to find keys that actually exist. --- 🔹 3️⃣ A Quick Example class Employee { String id; String name; public boolean equals(Object o) { return o instanceof Employee && id.equals(((Employee) o).id); } public int hashCode() { return id.hashCode(); } } Here, two employees with the same ID are considered equal — and because hashCode aligns with that logic, HashMap works perfectly. ✅ --- ⚡ The Takeaway Always override equals() and hashCode() together Use IDEs or Lombok (@EqualsAndHashCode) to generate them safely Test equality logic for correctness, not convenience They may look small — but they hold the Java Collection Framework together 🔗 --- 💬 Your turn: Have you ever faced a bug because of incorrect equals() or hashCode() implementation? 👇 Drop your story — I bet every dev has one! #Java #Collections #HashMap #CleanCode #BackendDevelopment #SoftwareEngineering #JavaDeveloper

🚀 #30DaysOfJava Challenge — 1 Java/Spring Project Per Day! Yesterday I kicked off the journey: Day 1/30 Project: User-Profile-Service — a user microservice inspired by real-world applications. And today, we move on to Day 2/30! Project: Content-Catalog-Service — a microservice handling content delivery and catalog management efficiently, designed to handle large datasets. 💡 Under the Hood: Pagination in APIs When building APIs, many developers implement pagination without thinking much about what happens internally. The truth is, understanding how your database handles OFFSET, LIMIT, and Pageable objects can make a huge difference in performance, especially as your dataset grows. 🎯 What I cover in today’s article on The Java Place: How the database executes OFFSET and LIMIT Why naive pagination can become a bottleneck for large tables Strategies for efficient pagination in Spring Boot, including practical tips 💡 Pro tip: Using Pageable instead of loading everything with findAll() drastically reduces memory usage — sometimes over 99% for large tables. Small change, big impact! ⚡ 🧩 Read the full article: 🔗 Pagination Under the Hood 💻 Check out the code: 🔗 GitHub Day 2 — Content Catalog Service 💬 Discussion time: What’s the trickiest pagination issue you’ve faced in Spring Boot? Do you prefer cursor-based, offset, or keyset pagination for large datasets? Let’s share experiences! 👇 🚀 Follow the #30DaysOfJava journey for daily hands-on Java/Spring projects and insights. #Java #SpringBoot #Backend #Pagination #DatabasePerformance #CleanCode #SoftwareEngineering #TheJavaPlace #30DaysOfJava

🔖 Annotations in Java: The Metadata That Powers Modern Frameworks Behind every clean, modern Java framework lies the silent power of annotations the metadata that tells the compiler and runtime what to do. Here’s what you’ll discover in this guide: ▪️What Annotations Really Are → Metadata that configures, documents, and automates behavior without altering logic. ▪️Built-in Annotations → @Override, @Deprecated, and @SuppressWarnings — your must-know compiler helpers. ▪️Custom Annotations → Create your own @interface annotations for validation, logging, or automation. ▪️Retention Policies → Learn where annotations live — at source, bytecode, or runtime. ▪️Target Types → Control where annotations can be applied — class, method, field, or parameter. ▪️Real-World Use Cases → See how Spring, Hibernate, and JUnit use annotations like @Autowired, @Entity, and @Test to simplify configuration. ▪️Interview Q&A → Understand retention, target, and runtime use — topics every Java interview covers. 📌 Like, Save & Follow CRIO.DO for more Java deep-dives made simple. 💻 Learn Java by Building Real Frameworks At CRIO.DO, you’ll master advanced Java concepts from annotations to dependency injection by actually building backend systems and Spring-based projects. 🚀 Book your FREE trial today- https://lnkd.in/geb_GYW2 and start coding like a pro! #Java #Annotations #CrioDo #LearnJava #SoftwareDevelopment #SpringFramework #Hibernate #JUnit #BackendEngineering #CodeSmart