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Top 30 Java Interview Questions & Answers for Infosys (3+ Years Experience) Updated for 2026 – Real-world explanations + examples Infosys interviews emphasize problem-solving , Java fundamentals , collection performance , and multithreading concepts . Below are the top 30 most commonly asked Java questions for 3–5 years experience , each with concise answers + real project examples .  Q1. What are the four major OOP concepts in Java? Answer: The four major object-oriented programming (OOP) concepts are: Encapsulation , Abstraction , Inheritance , Polymorphism .  Encapsulation : wrapping data (fields) and methods in a class, controlling access via modifiers (private/public). Abstraction : exposing only necessary details, hiding internal implementation. Inheritance : subclassing to reuse code. Polymorphism : objects taking many forms — e.g., method overloading (compile time) or overriding (runtime). Example: class Animal { public void sound () { ...

  🟢 30 Basic Java Interview Questions for Freshers (with Examples & Use Cases) If you are preparing for interviews in service-based companies like TCS, Infosys, Accenture, Wipro, Tech Mahindra , these are the most commonly asked Java interview questions for freshers (<1 year experience) . Each question has: ✅ Simple explanation ✅ Real-life use case ✅ Small code example 1. What are the main features of Java? Answer: Object-Oriented Platform Independent Simple, Secure, Robust Multithreaded & Portable 👉 Use Case: Run same .class file on Windows & Linux. public class HelloWorld { public static void main (String[] args) { System.out.println( "Java is platform independent!" ); } } 2. What is JVM, JRE, and JDK? Answer: JVM: Runs Java bytecode. JRE: Libraries + JVM. JDK: JRE + tools (javac, debugger). // javac HelloWorld.java → JDK compiles to bytecode // java HelloWorld → JRE runs program inside JVM 3....