Daniel Witkowski’s Post

It only takes a few lines of code to realize Java’s parameter passing isn’t as obvious as it first looks. Primitives behave one way, immutable objects another, and mutable objects can surprise you if you’re not paying attention to what’s actually being copied. If you’ve ever looked at a method call and wondered why the caller’s data changed, or didn’t, this article breaks down exactly what’s happening in the JVM. https://bit.ly/3OdJYV5

The Magic of @SneakyThrows in Java: How Does It Break the Rules? Lombok’s @SneakyThrows often raises questions in code reviews. It allows us to throw a checked exception (like IOException) without adding a throws clause - something Java normally forbids. The Problem: Java forces you to catch checked exceptions or declare them. This is especially frustrating with lambdas, where adding a throws declaration isn't an option. How does this work? Lombok uses bytecode manipulation. It replaces your checked exception with a generic throw that bypasses the compiler's checks. At runtime, the exception is thrown normally, but the compiler never sees the violation. It’s a clean solution for edge cases - just use it intentionally. While @SneakyThrows makes the code look cleaner, it breaks the method signature contract. Consumers of your method won't know they need to handle that exception, which can lead to unexpected application crashes. It also violates the Principle of Least Astonishment - other developers reading the code won't expect a checked exception to appear out of nowhere, making debugging and maintenance more difficult. But despite these risks, it's hard to deny how pleasant @SneakyThrows feels to use. The code becomes so clean and readable - no more wrapping everything in try-catch blocks just to satisfy the compiler. When you're working with streams or quick scripts, that single annotation removes the noise and lets the business logic shine. Do you use @SneakyThrows in your projects? Let’s discuss below! 👇 #Java #Programming #Lombok #SoftwareDevelopment #CodingTips

One subtle difference between Java and Rust that says everything about language philosophy. In Java, mutating a Map inside computeIfAbsent compiles fine — then explodes at runtime with a ConcurrentModificationException. In Java 8, it won't even crash. It silently corrupts your data. In Rust, the same pattern doesn't compile. At all. That's not a limitation. That's the point. I broke down both examples with the actual compiler output on my blog → https://lnkd.in/gqPgnebP #Rust #Java #SoftwareEngineering #MemorySafety

📘 Day 7 | Core Java – Concept Check🌱 Revising Core Java concepts and validating my understanding with answers 👇 1️⃣ Why does Java not support multiple inheritance with classes? -->To avoid ambiguity and complexity (diamond problem). Java achieves multiple inheritance using interfaces instead. 2️⃣ What happens if we override equals() but not hashCode()? -->It breaks the contract between equals() and hashCode(), causing incorrect behavior in hash-based collections like HashMap. 3️⃣ Can an abstract class have a constructor? Why? --> Yes, an abstract class can have a constructor to initialize common data when a subclass object is created. 4️⃣ Why is method overloading decided at compile time? --> Because it is resolved based on method signature (method name + parameters) at compile time, not at runtime. 5️⃣ What is the difference between method overriding and method hiding? --> Overriding happens with non-static methods at runtime, while hiding happens with static methods at compile time. 6️⃣ Why can’t we create an object of an abstract class? -->Because abstract classes may contain abstract methods without implementation, and objects must have complete behavior. 7️⃣ How does polymorphism help in reducing code dependency? --> It allows programming to interfaces or parent classes, making code flexible and easy to extend without modification. 8️⃣ What is the use of the instanceof operator in Java? --> It checks whether an object belongs to a specific class or interface at runtime. Learning concepts deeply by questioning and validating answers 📚💻 #CoreJava #JavaLearning #ProgrammingConcepts #LearningJourney #MCAGraduate

I wrote a blog post about "Functional Composition Patterns." If you're interested in learning how to implement them in pure Java, it's good material. You could also check out the rest of the documentation for the `dmx-fun` library. https://lnkd.in/eR5uvmHE

While solving a competitive programming problem, I revisited an interesting concept in Java’s BigInteger class — especially the meaning of certainty in isProbablePrime(). 🔹 Problem Statement Given a number n (which can be very large), determine whether it is prime or not prime. 📌 Note: The number may contain hundreds of digits, so primitive data types (int, long) are not sufficient. 🔹 Why normal prime checking fails ❌ Traditional logic like: using for loop and finding the primenumber for (int i = 2; i <= sqrt(n); i++) does not work because: 1. int / long overflow for large inputs 2. sqrt() cannot be calculated for huge numbers 3. Time complexity becomes impractical 🔹 Correct Approach using BigInteger Java provides a built-in method:-- isProbablePrime(int certainty)--- Here, certainty means: The level of confidence that the number is prime (The probability of error is less than 1 / 2^certainty) 🔹 Java Program (Competitive-ready) import java.io.*; import java.math.BigInteger; public class Solution { public static void main(String[] args) throws Exception { BufferedReader br = new BufferedReader( new InputStreamReader(System.in)); String n = br.readLine().trim(); BigInteger number = new BigInteger(n); if (number.isProbablePrime(1)) { System.out.println("prime"); } else { System.out.println("not prime"); } } } ✔️ Handles very large numbers ✔️ Passes hidden test cases ✔️ Fast and reliable 🔹 Key Learning 💡 certainty is not the number to test It controls how confident Java should be Even certainty = 1 is sufficient for most competitive platforms 📚 Takeaway: When dealing with very large numbers, rely on BigInteger’s probabilistic algorithms instead of manual prime-checking logic. #Java #BigInteger #CompetitiveProgramming #ProblemSolving #LearningEveryDay #CodingTips

Learn how to use Java’s var keyword with local variable type inference—best practices, pitfalls, and examples for cleaner, concise code.

💡 Java Tip: Using getOrDefault() in Maps When working with Maps in Java, we often need to handle cases where a key might not exist. Instead of writing extra conditions, Java provides a simple and clean method: getOrDefault(). 📌 What does it do? getOrDefault(key, defaultValue) returns the value for the given key if it exists. Otherwise, it returns the default value you provide. ✅ Example: Map<String, Integer> map = new HashMap<>(); map.put("apple", 10); map.put("banana", 20); System.out.println(map.getOrDefault("apple", 0)); // Output: 10 System.out.println(map.getOrDefault("grapes", 0)); // Output: 0 🔎 Why use it? • Avoids null checks • Makes code shorter and cleaner • Very useful for frequency counting problems 📊 Common Use Case – Counting frequency map.put(num, map.getOrDefault(num, 0) + 1); This small method can make your code more readable and efficient. Thankful to my mentor, Anand Kumar Buddarapu, and the practice sessions that continue to strengthen my core Java knowledge. Continuous learning is the key to growth! #Java #Programming #JavaDeveloper #CodingTips #SoftwareDevelopment

🚀 Mastering Core Java | Day 10 📘 Topic: Exception Handling Today’s session focused on Exception Handling, a critical concept in Java that helps manage runtime errors gracefully and ensures smooth program execution. 🔑 What is an Exception? An unexpected event that disrupts normal program flow Occurs during execution (e.g., invalid input, missing files, divide by zero) If not handled, it can cause program termination 🧠 Why Exception Handling is Important? Prevents application crashes Improves program reliability and stability Separates error-handling logic from core business logic Makes debugging and maintenance easier 🧩 Key Keywords in Exception Handling: try – Contains risky code catch – Handles the exception finally – Executes whether an exception occurs or not throw / throws – Used to explicitly pass exceptions Simple Syntax & Example: try { int result = 10 / 0; } catch (ArithmeticException e) { System.out.println("Cannot divide by zero"); } finally { System.out.println("Execution completed"); } 📌 Types of Exceptions: Compile‑Time (Checked) – Detected at compile time Examples: IOException, SQLException Run‑Time (Unchecked) – Occur during execution Examples: NullPointerException, ArrayIndexOutOfBoundsException, ArithmeticException 💡 Key Takeaway: Exception Handling allows applications to handle errors gracefully, improving user experience and making systems more robust. Grateful to my mentor Vaibhav Barde sir for the clear explanations and real‑world examples, which made this concept easy to understand and apply. 📈 Continuing to strengthen my Core Java and OOP fundamentals step by step. #ExceptionHandling #CoreJava #JavaLearning #Day10 #OOPConcepts #SoftwareDevelopment #LearningJourney #ProfessionalGrowth

☕ Java for-each Loop – Enhanced Loop Simplified The for-each loop (also called the enhanced for loop) in Java is a powerful repetition control structure that makes iterating over arrays and collections simple and readable. It is especially useful when: ✔ You need to execute a loop a specific number of times ✔ You want to iterate without using an index ✔ You don’t know the exact number of iterations 🔹 Syntax of for-each Loop for (declaration : expression) { // Statements } Execution Process: Declaration → A variable compatible with the array element type Expression → The array or collection being iterated The declared variable holds the current element during each iteration. 🔹 Example 1: Iterating Over a List of Integers List<Integer> numbers = Arrays.asList(10, 20, 30, 40, 50); for (Integer x : numbers) { System.out.print(x); System.out.print(","); } 📌 Output: 10, 20, 30, 40, 50, 🔹 Example 2: Iterating Over a List of Strings List<String> names = Arrays.asList("James", "Larry", "Tom", "Lacy"); for (String name : names) { System.out.print(name); System.out.print(","); } 📌 Output: James, Larry, Tom, Lacy, 🔹 Example 3: Iterating Over an Array of Objects Student[] students = { new Student(1, "Julie"), new Student(3, "Adam"), new Student(2, "Robert") }; for (Student student : students) { System.out.print(student); System.out.print(","); } This demonstrates how the enhanced for loop works seamlessly with custom objects as well. 💡 The for-each loop improves readability, reduces boilerplate code, and minimizes errors related to index handling. Mastering looping concepts is essential for writing clean and efficient Java programs. #Java #ForEachLoop #EnhancedForLoop #JavaProgramming #Collections #Arrays #Coding #FullStackJava #Developers #AshokIT