Mastering Java Stream API for Cleaner Code

📌 Java 8 Functional Interfaces — Explained with Use Cases Java provides built-in functional interfaces to support lambda expressions and functional programming. Here are the most important ones every Java developer should know: --- 1️⃣ Runnable @FunctionalInterface public interface Runnable {   void run(); } ✔ Takes: No input   ✔ Returns: Nothing  Use Case: • Multithreading tasks Example: Runnable r = () -> System.out.println("Task running"); --- 2️⃣ Callable @FunctionalInterface public interface Callable<V> {   V call() throws Exception; } ✔ Takes: No input   ✔ Returns: Result  Use Case: • Tasks that return values (ExecutorService) Example: Callable<Integer> c = () -> 10; --- 3️⃣ Comparator @FunctionalInterface public interface Comparator<T> {   int compare(T o1, T o2); } ✔ Takes: Two inputs   ✔ Returns: int  Use Case: • Sorting collections Example: list.sort((a, b) -> a - b); --- 4️⃣ Function<T, R> ✔ Takes: One input   ✔ Returns: One output  Use Case: • Transforming data Example: Function<String, Integer> f = s -> s.length(); --- 5️⃣ Predicate<T> ✔ Takes: One input   ✔ Returns: boolean  Use Case: • Filtering conditions Example: Predicate<Integer> p = x -> x > 10; --- 6️⃣ Consumer<T> ✔ Takes: One input   ✔ Returns: Nothing  Use Case: • Performing actions (printing, logging) Example: Consumer<String> c = s -> System.out.println(s); --- 7️⃣ Supplier<T> ✔ Takes: No input   ✔ Returns: Value  Use Case: • Lazy value generation Example: Supplier<Double> s = () -> Math.random(); --- 🧠 Quick Summary Runnable → No input, no output   Callable → No input, returns output   Function → Input → Output   Predicate → Input → boolean   Consumer → Input → action   Supplier → No input → output  --- 💡 Key Takeaway These interfaces form the backbone of Java 8 features like Streams and Lambdas. Mastering them helps write clean, functional, and expressive code. #Java #Java8 #FunctionalInterfaces #Lambda #BackendDevelopment

🚀 Java Evolution: From Java 8 to Java 25 (LTS) – Don’t Call It “Old” Yet! 👀 Think Java is just a relic of the past? Think again. It’s quietly become one of the most modern, scalable, and developer-friendly languages out there. Let’s take a whirlwind tour of its transformation. Buckle up! 🔍 🔹 Java 8 – The Revolution Begins (2014) This is where Java stopped being “that verbose enterprise thing” and started flexing. ✅ Lambdas & Functional Programming: Say hello to cleaner, expressive code. ✅ Stream API: Data processing got a functional makeover. ✅ Date & Time API: Finally, no more Calendar class nightmares. 🔹 Java 11 – Polished & Production-Ready (2018) Java shed some baggage and became a smoother ride. ✅ Standard HTTP Client: Networking without the third-party hassle. ✅ String & API Enhancements: Small tweaks, big quality-of-life wins. ✅ Developer Experience: Less friction, more focus. 🔹 Java 17 (LTS) – The Modern Backbone (2021) The go-to for most companies today. It’s stable, modern, and packed with goodies. ✅ Records: Boilerplate? What boilerplate? Data classes made easy. ✅ Sealed Classes: Control your inheritance like a pro. ✅ Pattern Matching for instanceof: Cleaner, smarter type checks. 🔹 Java 21 (LTS) – Concurrency King (2023) This is where Java redefined scalability. Mind-blowing stuff. ✅ Virtual Threads (Project Loom): Handle thousands of threads without breaking a sweat. ✅ Pattern Matching for switch: Logic so clean, it’s almost poetic. ✅ Sequenced Collections: Ordered data structures, done right. 🔹 Java 22 – Refining the Craft (2024) Java keeps trimming the fat, making life easier for devs. ✅ Unnamed Variables & Patterns: Less typing, more doing. ✅ Stream API Enhancements: Even more power for data wrangling. ✅ String Templates (Preview): Formatting strings without the mess. 🔹 Java 25 (LTS) – Future-Proofed & Ready (2025) The next frontier (based on current roadmaps and speculation). ✅ Advanced Pattern Matching: Code that reads like plain English. ✅ Performance & Garbage Collection Boosts: Faster, leaner, meaner. ✅ Virtual Thread Ecosystem: Concurrency on steroids. ✅ Expressive Syntax: Java, but somehow even prettier. 💡 Key Takeaway from This Journey: Java isn’t just about “write once, run anywhere” anymore. It’s a powerhouse of performance, scalability, and developer productivity. Ignore the memes – this language is thriving. 📌 If You’re Learning Java Today: Master Java 17 for a solid foundation (it’s the current LTS sweet spot). Get comfy with Java 21 for cutting-edge features like Virtual Threads. Keep an eye on Java 25 – it’s where the future is heading. 👇 Drop a Comment: Which Java version are you rocking right now? Are you hyped for Java 25, or sticking with the tried-and-true? Let’s chat! #Java #SoftwareEngineering #BackendDevelopment #JavaDeveloper #Programming #Coding #Tech #Developers #Learning #CareerGrowth

🚀 JAVA METHOD TYPES — MASTER THE CORE OF CLEAN CODE In Java, methods are not just functions — they are the building blocks of reusable, scalable, and maintainable systems. If you want to write production-grade code, understanding method types is non-negotiable. 🔹 1. Static Methods ✔ Belong to the class, not objects ✔ Memory efficient & fast access ✔ Called without creating an instance 💡 Use case: Utility or helper functions class MathUtils {   static int add(int a, int b) {     return a + b;   } } 🔹 2. Instance Methods ✔ Require object creation ✔ Can access instance variables ✔ Core of OOP behavior 💡 Use case: Business logic tied to object state class User {   String name;       void display() {     System.out.println(name);   } } 🔹 3. Abstract Methods ✔ Declared without implementation ✔ Must be implemented by subclasses ✔ Enables abstraction 💡 Use case: Define blueprint for classes abstract class Animal {   abstract void sound(); } 🔹 4. Final Methods ✔ Cannot be overridden ✔ Ensures behavior consistency 💡 Use case: Security-sensitive or fixed logic class Bank {   final void secureTransaction() {     System.out.println("Verified");   } } 🔹 5. Synchronized Methods ✔ Thread-safe execution ✔ Prevents race conditions 💡 Use case: Multi-threaded environments synchronized void updateBalance() {   // critical section } 🔹 6. Default Methods (Interface) ✔ Introduced in Java 8 ✔ Allow method body in interfaces 💡 Use case: Backward compatibility interface Vehicle {   default void start() {     System.out.println("Starting...");   } } 🔹 7. Private Methods (Interface) ✔ Reusable internal logic inside interfaces ✔ Cleaner code structure 🔹 8. Overloaded Methods ✔ Same method name, different parameters ✔ Compile-time polymorphism 💡 Use case: Flexibility in API design int sum(int a, int b) { return a + b; } int sum(int a, int b, int c) { return a + b + c; } 🔥 FINAL TAKEAWAY Mastering Java method types = ✔ Cleaner architecture ✔ Better performance ✔ Scalable applications ✔ Interview dominance 💬 CTA Which method type do you use the most in your projects? Comment below 👇 📌 HASHTAGS #Java #JavaProgramming #Coding #SoftwareEngineering #BackendDevelopment #OOP #ProgrammingTips #JavaDeveloper #TechSkills #LearnJava

Let’s talk about Optional in Java. ☕ When should you use it, and when should you avoid it? Recently, I saw a post suggesting using Optional as a method parameter to simulate Kotlin's Elvis operator (?:). This is actually an anti-pattern! Let's review when to use it and when to avoid it, inspired by Stuart Marks’s famous talk on the topic. What’s the actual problem with null in Java? It’s semantic ambiguity: is it an error, an uninitialized variable, or a legitimate absence of a value? This forces us into defensive coding (if (obj != null)) to avoid the dreaded NPEs. Java introduced Optional<T> to declare a clear API contract: "This value might not be present; it's your responsibility to decide how to handle its absence." ✅ WHERE TO USE OPTIONAL: 👉 Method Return Types: This is its primary design purpose. It clearly communicates that a result might be empty: Optional<SaleEntity> findSaleById(Long id) 👉 Safe Transformations: Extract nested data without breaking your flow with intermediate null checks: var city = Optional.ofNullable(client) .map(Client::getAddress) .map(Address::getCity) .orElse("Unknown"); 👉 Stream Pipelines: Using flatMap(Optional::stream) elegantly filters a stream, leaving only the present values without cluttering your code. ❌ WHERE NOT TO USE OPTIONAL (ANTI-PATTERNS): 👉 Method Parameters: Never do this. It complicates the signature, creates unnecessary object allocation, and doesn't even prevent someone from passing a null instead of an Optional! Use internal validations (Objects.requireNonNull). 👉 Calling .get() without checking: Never call Optional.get() unless you can mathematically prove it contains a value. Prefer alternatives like .orElse(), .orElseGet(), or .ifPresent(). 👉 Returning Null for an Optional: If your method returns an Optional, returning a literal null defeats the entire purpose and will cause unexpected NPEs downstream. Always return Optional.empty(). 👉 Class Fields (Attributes): Optional is not Serializable. Use a documented null or the "Null Object Pattern". 👉 Collections: Never return Optional<List<T>>. Just return an empty list (Collections.emptyList()). It's semantically correct and saves memory. Optional doesn't eradicate null, but it helps us design more honest APIs. Let's use it responsibly. 🛠️ To dive deeper, I've attached a PDF summary of the core rules for Optionals. 📄👇 What other anti-patterns have you seen when using Optionals? Let me know below! (PS: I'll leave the link to Stuart Marks's full video breakdown in the first comment). #Java #SoftwareEngineering #CleanCode #Backend #JavaDeveloper #Optional

Java Streams Java Streams are not just a feature… They changed how we process collections — from imperative to declarative programming. If you’re preparing for interviews or writing clean code, this is a must 👇 ⸻ 🔥 What is a Stream? 👉 A Stream is a sequence of elements that supports functional-style operations. ✔ Does NOT store data ✔ Processes data from collections ✔ Supports chaining ⸻ ⚡ 3 Types of Operations 1️⃣ Intermediate Operations (Return Stream) These are lazy — executed only when terminal operation is called. ⸻ 🔹 filter() 👉 Filters elements based on condition list.stream().filter(x -> x > 10); ⸻ 🔹 map() 👉 Transforms each element list.stream().map(x -> x * 2); ⸻ 🔹 flatMap() 👉 Flattens nested structures list.stream().flatMap(x -> x.stream()); ⸻ 🔹 distinct() 👉 Removes duplicates list.stream().distinct(); ⸻ 🔹 sorted() 👉 Sorts elements list.stream().sorted(); ⸻ 🔹 limit() 👉 Limits number of elements list.stream().limit(5); ⸻ 🔹 skip() 👉 Skips elements list.stream().skip(2); ⸻ 🚀 Terminal Operations (Return Result) These trigger execution. ⸻ 🔹 forEach() 👉 Iterates elements list.stream().forEach(System.out::println); ⸻ 🔹 collect() 👉 Converts stream to collection list.stream().collect(Collectors.toList()); ⸻ 🔹 count() 👉 Counts elements list.stream().count(); ⸻ 🔹 findFirst() / findAny() 👉 Returns element list.stream().findFirst(); ⸻ 🔹 anyMatch() / allMatch() / noneMatch() 👉 Condition checks list.stream().anyMatch(x -> x > 10); ⸻ 🔹 reduce() 👉 Combines elements list.stream().reduce((a, b) -> a + b); ⸻ 💡 Optional but Important 🔹 peek() 👉 Debugging / intermediate action list.stream().peek(System.out::println); ⸻ 🔥 Example (Real Interview Level) List<Integer> list = Arrays.asList(1,2,3,4,5,6); List<Integer> result = list.stream() .filter(x -> x % 2 == 0) .map(x -> x * x) .collect(Collectors.toList()); 👉 Output: [4, 16, 36] ⸻ ⚠️ Common Mistakes ❌ Forgetting terminal operation ❌ Using streams for very simple loops ❌ Modifying source inside stream ⸻ 🎯 When to Use Streams? ✔ Data transformation ✔ Filtering & aggregation ✔ Writing clean and readable code ⸻ 🚀 Final Thought Streams are not about writing less code… They are about writing expressive and maintainable code ⸻ 💬 Question: Which Stream method do you use the most in your daily work? #Java #JavaStreams #SDET #AutomationTesting #InterviewPreparation

🔥 Core Java (Must Prepare) 1. What is the difference between == and .equals()? == → compares reference (memory location) .equals() → compares content/value 2. Why String is immutable? Security (used in DB, network, etc.) Thread-safe String pool optimization 3. What is String Pool? A memory area in heap where unique String literals are stored. Avoids duplicate objects → improves performance 4. Difference: ArrayList vs LinkedList FeatureArrayListLinkedListStructureDynamic ArrayDoubly Linked ListAccessFastSlowInsert/DeleteSlowFast 5. How HashMap works internally? Uses hashing (hashCode + equals) Stores data in buckets Collision handled using: LinkedList (Java 7) Tree (Java 8 → Balanced Tree) 6. Difference: HashMap vs ConcurrentHashMap HashMap → not thread-safe ConcurrentHashMap → thread-safe (segment locking / CAS) 🔥 OOP & Design 7. What are OOP principles? Encapsulation Inheritance Polymorphism Abstraction 8. Method Overloading vs Overriding Overloading → same method name, different parameters Overriding → runtime polymorphism (same method in subclass) 9. What is SOLID principle? S → Single Responsibility O → Open/Closed L → Liskov Substitution I → Interface Segregation D → Dependency Injection 🔥 Multithreading (VERY IMPORTANT) 10. What is Thread? Lightweight process for parallel execution 11. Runnable vs Callable Runnable → no return Callable → returns value + throws exception 12. What is Synchronization? Prevents multiple threads accessing same resource 13. What is Deadlock? When threads are waiting on each other forever 14. What is Executor Framework? Manages thread pool → improves performance 15. What is volatile keyword? Ensures visibility of changes across threads 🔥 Java 8+ (VERY IMPORTANT) 16. What is Lambda Expression? Short way to write functional code (list) -> list.size() 17. What is Functional Interface? Interface with one abstract method Example: Runnable 18. Stream API? Used for data processing (filter, map, reduce) 19. Optional class? Avoids NullPointerException 🔥 Exception Handling 20. Checked vs Unchecked Exception Checked → compile-time (IOException) Unchecked → runtime (NullPointerException) 21. Difference: throw vs throws throw → used to throw exception throws → declares exception 🔥 Memory & JVM 22. What is JVM? Executes Java bytecode 23. Heap vs Stack Heap → Objects Stack → Method calls, variables 24. What is Garbage Collection? Automatically removes unused objects 🔥 Advanced (4+ Year Level) 25. What is Serialization? Convert object → byte stream 26. transient keyword? Skips variable during serialization 27. Comparable vs Comparator Comparable → natural sorting Comparator → custom sorting 28. Fail-fast vs Fail-safe Fail-fast → throws exception (ArrayList) Fail-safe → works on copy (ConcurrentHashMap) 🔥 Real Interview Scenario Questions 29. How do you handle high traffic in Java? Caching (Redis) Thread pool Load balancing 30. How do you debug production issue? Logs (ELK) Thread dump Heap dump

Asynchronous Programming in Java Java Level Async (Core Concepts) ✅ Runnable vs Callable At the very basic level, when you create a task: Runnable → Just runs something, doesn’t return anything Callable → Runs something and gives you a result back In real projects: Use Runnable for things like logging, background audit, notifications Use Callable when you’re calling a DB or another API and need a response Example: Runnable r = () -> System.out.println("Logging task"); Callable<String> c = () -> { return "DB Data"; }; ✅ Executor This is a very simple interface — just executes a task. In reality, you won’t use this directly much. It’s more like a base concept behind everything else. Example: Executor ex = Runnable::run; ex.execute(() -> System.out.println("Task executed")); ✅ ExecutorService (Very Important) This is where real-world usage starts. Instead of creating threads manually (which is costly), we use a thread pool. Why? Thread creation is expensive Reusing threads improves performance You get control over how many tasks run in parallel Typical scenarios: Processing thousands of records Calling multiple APIs in parallel Running batch jobs Example: ExecutorService ex = Executors.newFixedThreadPool(3); ex.submit(() -> { System.out.println(Thread.currentThread().getName()); }); ✅ Executors (Factory Class) 👉 Utility class to create thread pools Types: Fixed → Controlled threads Cached → Dynamic threads Single → Sequential execution Executors.newFixedThreadPool(5); Executors.newCachedThreadPool(); ->Quick setup (POC / small apps) ->Avoid direct use in production → use custom thread pool ✅ Future (Old Approach) ->Represents async result ->get() blocks the thread Future<String> f = ex.submit(() -> "Hello"); String res = f.get(); // blocks ->Blocking → reduces performance ->Legacy systems only ✅ CompletableFuture ⭐⭐⭐ (MOST IMPORTANT) ->Modern async API (Java 8+) Supports: Non-blocking execution Chaining Combining multiple tasks Exception handling CompletableFuture.supplyAsync(() -> "User") .thenApply(name -> name + " Data") .thenAccept(System.out::println); ->Parallel Calls Example CompletableFuture<String> f1 = CompletableFuture.supplyAsync(() -> "Orders"); CompletableFuture<String> f2 = CompletableFuture.supplyAsync(() -> "Payments"); CompletableFuture.allOf(f1, f2).join(); =>Real Scenarios: Aggregating microservice responses Calling multiple APIs in parallel Building dashboards =>Why it's powerful? Non-blocking → better performance Functional style → clean code ✅ ForkJoinPool -> Uses divide & conquer approach ForkJoinPool pool = new ForkJoinPool(); ->When to use? Large computations Recursive parallel processing ->Example: File parsing Data splitting tasks Spring level async techniques are upcoming post. #java #springboot #javadevelopement #spring #springboot #programming #coding

🚀 Day 44 – Core Java | Functional Interfaces, Lambda Expressions & Java Execution Today’s session connected multiple advanced Java concepts and clarified how modern Java simplifies coding while maintaining performance. 🔹 Functional Interface A Functional Interface is an interface that contains only one abstract method. Example: @FunctionalInterface interface Vehicle { void ride(); } Functional interfaces are important because they enable lambda expressions and modern functional-style programming in Java. Common examples from Java API: Runnable Comparable Comparator 🔹 Ways to Implement a Functional Interface We explored four different approaches: 1️⃣ Regular Class class Bicycle implements Vehicle { public void ride() { System.out.println("Pedal the cycle"); } } 2️⃣ Inner Class Class defined inside another class for better encapsulation. 3️⃣ Anonymous Inner Class A class without a name, created and used at the same location. 4️⃣ Lambda Expression (Modern Approach) Vehicle v = () -> { System.out.println("Pedal the cycle"); }; Lambda expressions help reduce boilerplate code and make programs more concise. 🔹 Key Rules of Lambda Expressions ✔ Works only with functional interfaces ✔ Can remove method signature because interface has only one abstract method ✔ Parameter types are optional in many cases ✔ Parentheses are optional when there is one parameter Example: (a) -> System.out.println(a); 🔹 Java Program Execution (Refresher) We also revisited how a Java program executes internally: .java file (High-Level Code) ↓ Java Compiler (javac) ↓ .class file (Bytecode) ↓ JVM ↓ JIT Compiler ↓ Machine Code ↓ Output Key components involved: JVM (Java Virtual Machine) Class Loader JIT Compiler (Just-In-Time Compiler) Because Java uses both compiler and interpreter concepts, it is often called a hybrid programming language. 🔹 Syntax Errors vs Exceptions Another important distinction: ✔ Syntax Error Occurs during compilation time due to faulty coding. Example: System.out.prinln("Hello"); ✔ Exception Occurs during runtime due to faulty input or unexpected situations. Example: ArithmeticException NullPointerException ArrayIndexOutOfBoundsException 💡 Key Takeaway Understanding functional interfaces, lambda expressions, and Java execution flow builds the foundation for advanced topics like multithreading, streams, and modern Java frameworks. Next concept starting: Exception Handling. #Day44 #CoreJava #JavaLearning #LambdaExpression #FunctionalInterface #JavaProgramming #DeveloperJourney #JavaOOPS

Hello Connections, Post 17 — Java Fundamentals A-Z ☕ Java Streams have completely transformed coding approach. 🚀 However, many developers still have misconceptions about what a Stream truly is. Let's clear the air! 💡 🚫 What a Stream is NOT: ❌ A data structure ❌ A place to store data ❌ Anything like an ArrayList ✅ What a Stream actually IS: 🌊 A pipeline that processes data 📖 Reads from a source ⚙️ Transforms it step by step 🏁 Produces a result Example in Action: 💻 List<String> names = Arrays.asList("Alice", "Bob", "Charlie", "David"); long count = names.stream() // 1. SOURCE 📥 .filter(n -> n.length() > 3) // 2. INTERMEDIATE ⚙️ .count(); // 3. TERMINAL 🏁 System.out.println(count); // Output: 3 ⚠️ The Golden Rule: Streams are LAZY! 😴 Stream<String> stream = names.stream() .filter(n -> { System.out.println("Checking: " + n); return n.length() > 3; }); // 🤫 Nothing happens yet! stream.count(); // 🔥 NOW it runs! This laziness is a superpower—it avoids unnecessary processing, even in pipelines with millions of records! ⚡ 🧠 Quick Quiz — Test Your Knowledge! Problem 1 — What is the output? 🔢 List<Integer> nums = Arrays.asList(1, 2, 3, 4, 5); long result = nums.stream().filter(n -> n > 2).count(); System.out.println(result); 👉 Answer: 3 (Numbers 3, 4, and 5 pass the filter!) Problem 2 — How many times does filter run? ⏱️ List<String> names = Arrays.asList("Alice", "Bob", "Charlie"); Optional<String> result = names.stream() .filter(n -> n.startsWith("C")) .findFirst(); 👉 Answer: 3 times (Alice ❌, Bob ❌, Charlie ✅... then it stops!) Problem 3 — Will this print anything? 🙊 List<Integer> nums = Arrays.asList(1, 2, 3); Stream<Integer> stream = nums.stream() .filter(n -> n > 1) .map(n -> n * 2); 👉 Answer: Nothing! Remember: No terminal operation = No execution! 🚫 Post 17 Summary: 📝 🔴 Unlearned → "Stream is just another collection." 🟢 Relearned → "Stream is a lazy processing pipeline." 🤯 Biggest surprise → filter() does NOTHING without a terminal operation! Follow along for more👇 #Java #JavaFundamentals #BackendDevelopment #LearningInPublic #SDE2 #CodingTips #SoftwareEngineering

🚀 Understanding Generics in Java – Write Flexible & Type-Safe Code If you’ve ever worked with collections like List or Map, you’ve already used Generics — one of the most powerful features in Java. 🔹 What are Generics? Generics allow you to write classes, interfaces, and methods with a placeholder for the data type. This means you can reuse the same code for different data types while maintaining type safety. 🔹 Why use Generics? ✔️ Eliminates type casting ✔️ Provides compile-time type safety ✔️ Improves code reusability ✔️ Makes code cleaner and more readable 🔹 Simple Example: List<String> names = new ArrayList<>(); names.add("Sneha"); // names.add(10); ❌ Compile-time error 🔹 Generic Class Example: class Box<T> { private T value; public void set(T value) { this.value = value; } public T get() { return value; } } 🔹 🔥 Advanced Concepts Explained 🔸 1. Bounded Types (Restricting Types) You can limit what type can be passed: class NumberBox<T extends Number> { T value; } 👉 Only Integer, Double, etc. are allowed (not String) 🔸 2. Wildcards (?) – Flexibility in Collections ✔️ Unbounded Wildcard List<?> list; 👉 Can hold any type, but limited operations ✔️ Upper Bounded (? extends) List<? extends Number> list; 👉 Accepts Number and its subclasses 👉 Used when reading data ✔️ Lower Bounded (? super) List<? super Integer> list; 👉 Accepts Integer and its parent types 👉 Used when writing data 💡 Rule: PECS → Producer Extends, Consumer Super 🔸 3. Generic Methods public <T> void print(T data) { System.out.println(data); } 👉 Works independently of class-level generics 🔸 4. Type Erasure (Important for Interviews) Java removes generic type info at runtime: List<String> → List 👉 No runtime type checking 👉 Only compile-time safety 🔸 5. Multiple Bounds <T extends Number & Comparable<T>> 👉 A type must satisfy multiple conditions 🔸 6. Restrictions of Generics ❌ Cannot use primitives (int, double) → use wrappers ❌ Cannot create generic arrays ❌ Cannot use instanceof with generics 💡 Final Insight: Generics are not just a feature—they are a design tool that helps build scalable, reusable, and maintainable applications. Mastering advanced concepts like wildcards and type erasure can set you apart as a strong Java developer. #Java #Generics #AdvancedJava #Programming #JavaDeveloper #Coding #TechInterview