Java Two Sum Problem Solution with HashMap Optimization

🚀 Java Core Interview Series – Part 5 Polymorphism Explained Polymorphism is one of the most important concepts in Object-Oriented Programming (OOP) and is widely used in real backend development. In this post, I explained: 🔹 What is Polymorphism in Java 🔹 Types of Polymorphism (Compile-time & Runtime) 🔹 Method Overloading and Method Overriding 🔹 Key differences for interviews 🔹 Code examples for better understanding 🔹 Backend perspective in Spring Boot 💡 In real-world backend systems, polymorphism helps developers write flexible, reusable, and scalable code. For example, in Spring Boot we often program to interfaces rather than implementations, allowing different classes to provide their own behavior while keeping the same method structure. ⚡ Polymorphism = Flexibility + Reusability + Scalable Backend Design If you're preparing for Java or Backend interviews, understanding this concept is very important. Follow for more Java Backend & System Design concepts. #Java #OOP #Polymorphism #SpringBoot #BackendDevelopment #JavaDeveloper #Programming #SoftwareEngineering #LearnInPublic

This was a question I was recently asked in an interview: 👉 Is Java a purely object-oriented language? At first glance, many people say “Yes” because Java strongly follows core OOPS principles: • Encapsulation • Inheritance • Polymorphism • Abstraction However, the correct answer is: Java is not a purely object-oriented language. Here’s why: • Java supports primitive data types like int, double, char, and boolean, which are not objects. • We can define and use static methods and variables without creating objects. In a purely object-oriented language, everything must be treated as an object. Java is strongly object-oriented, but not purely object-oriented. Conceptual questions like this often test clarity of fundamentals more than coding ability. #Java #OOPS #InterviewPreparation #SoftwareEngineering #BackendDevelopment

🚀 Java Interview Question Series What is the difference between HashMap and ConcurrentHashMap? HashMap: ❌ Not thread safe ❌ Multiple threads can modify data simultaneously ConcurrentHashMap: ✅ Thread safe ✅ Allows concurrent read/write operations Used in multithreaded environments. Many developers fail this simple interview question. Follow me for more Java interview questions and coding tips. 💻 #Java #Programming #CodingInterview #SoftwareDevelopment

✅ LeetCode — Remove Duplicates from Sorted Array | Solved in Java! Another problem down, one step closer to the goal. 💪 🔍 Problem: Remove duplicates from a sorted array in-place. 💡 My Approach: Used a HashSet to filter unique elements, then wrote them back into the array and sorted the result — clean, readable, and efficient. 📊 Results: • Runtime: 8 ms (beats 3.87%) • Memory: 46.56 MB (beats 87.88% 🏆) 🚀 Key takeaway: Sometimes the simplest solution is the clearest one. Understanding the problem deeply matters more than clever tricks. Consistency is everything. One problem at a time, one day at a time. If you're also grinding LeetCode or preparing for interviews, let's connect and grow together! 🤝 #LeetCode #Java #DSA #DataStructures #Algorithms #CodingInterview #ProblemSolving #SoftwareEngineering #100DaysOfCode #CompetitiveProgramming #TechCareers

🚀 Java Core Interview Series – Part 4 Abstraction Explained Abstraction is one of the most important concepts in Object-Oriented Programming (OOP) and is widely used in real backend development. In this post, I explained: 🔹 What is Abstraction in Java 🔹 Real-life example (ATM machine) 🔹 Abstract Class vs Interface 🔹 Key differences for interviews 🔹 Code examples for better understanding 🔹 Backend perspective in Spring Boot 💡 In real-world backend systems, abstraction helps developers build clean, modular, and loosely coupled architectures. For example, in Spring Boot we often depend on interfaces instead of implementations, which enables Dependency Injection and scalable system design. ⚡ Strong Abstraction = Loose Coupling + Scalable Backend Architecture If you're preparing for Java or Backend interviews, understanding this concept is very important. Follow for more Java Backend & System Design concepts. #Java #OOP #Abstraction #SpringBoot #BackendDevelopment #JavaDeveloper #Programming #SoftwareEngineering #LearnInPublic

Overriding equals() vs hashCode() in Java This is a VERY important interview question for Java placements and LinkedIn interviews. It is mainly asked in Collections topic (especially with HashMap, HashSet). 🔹 1️⃣ equals() Method Defined in java.lang.Object Used to compare content equality Default implementation compares memory address 🔹 2️⃣ hashCode() Method Also defined in java.lang.Object Returns integer hash value Used internally by hashing collections like: HashMap HashSet Hashtable So: 👉 equals() checks equality 👉 hashCode() decides bucket location 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 #Collections  #BackendDevelopment  #Coding

🚀 Learning Series – Post #13 Today’s topic: Top 7 Java Interview Questions Asked in Companies If you're preparing for Java developer or backend roles, these are some of the most commonly asked interview questions. 1️⃣ What is Java? Java is a high-level, object-oriented programming language used to build scalable and platform-independent applications. 2️⃣ What is JVM? JVM (Java Virtual Machine) is responsible for running Java programs and converting bytecode into machine code. 3️⃣ What is JDK vs JRE? • JDK (Java Development Kit) → Used for development • JRE (Java Runtime Environment) → Used to run Java programs 4️⃣ What is OOP? OOP is a programming paradigm based on objects and classes, focusing on reusability and modularity. 5️⃣ What is Exception Handling? It is a mechanism to handle runtime errors using try-catch blocks. 6️⃣ What is Multithreading? It allows multiple threads to run concurrently, improving performance. 7️⃣ What is Collection Framework? It is a set of classes and interfaces used to store and manipulate data (e.g., List, Set, Map). 💡 Tip: Don’t just memorize answers — understand concepts and explain with examples in interviews. 📌 Next Post: Difference Between HashMap vs HashTable #LearningInPublic #JavaDeveloper #TechInterviews #BackendDevelopment #CareerGrowth

Hey Guys! 👋 Day 6 of revising my core Java fundamentals! ☕ Today, I explored Logical Operators and stumbled upon an absolute goldmine of a senior-level interview question! We all know the basics of the Logical AND (&&) and Logical OR (||) operators. They are used to evaluate boolean expressions (True/False). But the real magic happens under the hood with a concept called Short-Circuiting. ⚡ What is Short-Circuiting? Java is designed to be highly optimized. 🟢 If you use && (AND), Java knows that if the first condition is false, the entire expression will definitely be false. So, it completely skips evaluating the second condition to save time!. 🟢 If you use || (OR), Java knows that if the first condition is true, the whole expression is automatically true. Again, it ignores the second condition entirely!. This is fantastic for performance and is used 99% of the time in real-world programming. ❓ The Interview Question: An interviewer might ask: "What if I WANT both conditions to be evaluated, no matter what? Can you force Java to turn off short-circuiting?" Most developers would be stumped, but here is the mind-blowing trick I learned today: You can use Bitwise Operators on Boolean Expressions! 🧠 Normally, Bitwise operators like the single & and single | are strictly used to manipulate 0s and 1s at the memory level. But in Java, if you place a single & between two boolean expressions, it acts exactly like a logical AND, but with one massive difference: it does NOT short-circuit!. If you write (A < B) & (A < C), Java is forced to evaluate both sides completely, even if the first condition already failed!. Why does this matter? While you might rarely write this in a standard application, knowing that Bitwise operators can hijack logical expressions to prevent short-circuiting proves you understand Java's compilation behavior at a micro-level. It is a brilliant way to stand out in technical interviews! Did you know that Bitwise operators could be used on boolean conditions like this? Let’s discuss in the comments! 👇 #Java #SoftwareEngineering #LogicalOperators #TechFundamentals #StudentDeveloper #ComputerScience #InterviewPrep #CodingJourney #TechCareers

🚀 A Java Interview Experience Recently had an interesting technical discussion for a Java-based role. The conversation was not limited to basic theory it focused more on understanding how things work internally and how concepts are applied in real applications. The discussion started around my projects and gradually moved into deeper Java and backend concepts. Some of the topics and questions that came up: • How HashMap works internally and how collisions are handled • Difference between fail-fast and fail-safe iterators in Java Collections • What happens inside the JVM when a Java program runs • Explain Garbage Collection mechanisms and different GC types • Difference between Comparable and Comparator with use cases • How multithreading works in Java and difference between Runnable and Thread • What are synchronization issues and race conditions • How REST APIs are designed in backend applications • Writing optimized SQL queries with JOINs and indexing concepts • Discussion around project architecture and design decisions What stood out was that the focus was not just on answers, but on how well concepts are understood and explained with practical scenarios. Experiences like this always help in identifying areas to improve and strengthening the overall understanding of backend development. Looking forward to more such technical discussions and continuous learning. #Java #BackendDevelopment #InterviewExperience #SoftwareEngineering #JavaDeveloper #TechLearning

Hey everyone! 👋 Day 14 of my deep dive into core Java fundamentals! ☕ Today, I uncovered a massively popular "trick" interview question about Java's core identity. If you claim to know Object-Oriented Programming (OOP), an interviewer will almost certainly test you with this! 🧠 𝗧𝗵𝗲 𝗧𝗿𝗶𝗰𝗸𝘆 𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄 𝗤𝘂𝗲𝘀𝘁𝗶𝗼𝗻❓: Is Java a 100% purely Object-Oriented Programming language? 💡 The Trap & The Answer: Because Java forces us to put almost everything inside Classes, most beginners confidently answer "Yes!". But if you say that in an interview, you fell into the trap! 🪤 The correct answer is 𝗡𝗢. Java is only almost completely Object-Oriented. What is happening Under the Hood? In a strictly 100% pure OOP language, absolutely everything must be an Object. However, Java has a dual nature. To keep the language fast and optimized, the creators included Primitive Data Types (like int, float, boolean, and char). These primitives are NOT objects!. They don't require the new keyword to be created. They are static memory allocations that live directly in the Stack, completely bypassing the Heap memory where real Objects live. Because Java relies on these non-object primitives to function, it disqualifies itself from being a 100% pure OOP language! 🌟 𝗠𝘆 𝗚𝗼𝗹𝗱𝗲𝗻 𝗥𝘂𝗹𝗲 𝗳𝗼𝗿 𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄𝘀: Always remember: Classes (like Student) are Non-Primitive "User-Defined" Objects, but basic numbers and characters are just Primitives. This mix is exactly why Java is not purely OOP! #Java #SoftwareEngineering #TechFundamentals #StudentDeveloper #ComputerScience #InterviewPrep #OOP #TechCareers