Top 2000 Java Interview Questions and Answers for Freshers & Experts (2025)

Top 40 Java Interview Questions and Answers for Freshers & Experts (2025)

Are you preparing for your next Java interview in 2025? We’ve compiled over 2000 most important Java interview questions with accurate answers to help you crack your coding round, HR interview, and technical screening process. These questions cover all key Java topics including OOPs, Collections, Exceptions, Multithreading, JDBC, Java 8 Features, Spring Framework, and more!

📘 Sample Java Interview Questions (Core Java)

Top 200 Java Interview Questions and Answers

Q1: What is Java?

A: Java is a high-level, class-based, object-oriented programming language designed to have as few implementation dependencies as possible.

Q2: What is the JVM?

A: JVM (Java Virtual Machine) is an engine that provides a runtime environment to execute Java bytecode.

Q3: What is the JRE?

A: JRE (Java Runtime Environment) provides libraries, Java Virtual Machine (JVM), and other components to run applications written in Java.

Q4: What is the JDK?

A: JDK (Java Development Kit) is a software development kit used to develop Java applications. It includes JRE and development tools.

Q5: What are the features of Java?

A: Platform-independent, Object-Oriented, Simple, Secure, Robust, Architecture-neutral, Portable, High-performance, Interpreted, Multithreaded.

Q6: What is the difference between JDK, JRE, and JVM?

A: JDK includes JRE and development tools. JRE includes JVM and runtime libraries. JVM runs the bytecode.

Q7: What is a class in Java?

A: A class is a blueprint from which individual objects are created. It defines attributes and behaviors.

Q8: What is an object in Java?

A: An object is an instance of a class and contains state (fields) and behavior (methods).

Q9: What is a constructor?

A: A constructor is a special method used to initialize objects. It has the same name as the class.

Q10: What is inheritance?

A: Inheritance is a mechanism where one class acquires the properties and behaviors of a parent class.

Q11: What is polymorphism?

A: Polymorphism allows objects to be treated as instances of their parent class. It supports method overloading and overriding.

Q12: What is encapsulation?

A: Encapsulation is the wrapping of data and code into a single unit, like a class, and restricting access using access modifiers.

Q13: What is abstraction?

A: Abstraction hides complex implementation details and shows only the necessary features of an object.

Q14: What are access modifiers?

A: Access modifiers define the scope of accessibility for classes, variables, methods, and constructors. (public, private, protected, default)

Q15: What is the difference between method overloading and method overriding?

A: Overloading allows multiple methods with the same name but different parameters. Overriding means redefining a superclass method in a subclass.

Q16: What is an interface?

A: An interface is a reference type in Java that can contain only constants, method signatures, default methods, static methods, and nested types.

Q17: What is an abstract class?

A: An abstract class is a class that cannot be instantiated and can contain abstract methods which are implemented by subclasses.

Q18: What is a package in Java?

A: A package is a namespace that organizes a set of related classes and interfaces.

Q19: What is the difference between ‘==’ and ‘equals()’ in Java?

A: ‘==’ compares object references, while ‘equals()’ compares the content of the objects.

Q20: What are static methods and static variables?

A: Static members belong to the class rather than any instance. Static methods can be called without creating an instance.

Q21: What is the main() method in Java?

A: It is the entry point for any standalone Java application. It has the signature public static void main(String[] args).

Q22: What is a wrapper class in Java?

A: Wrapper classes convert Java primitives into objects. Examples: Integer, Double, Character.

Q23: What is autoboxing and unboxing?

A: Autoboxing converts primitives to wrapper classes automatically. Unboxing is the reverse.

Q24: What is the final keyword in Java?

A: It can be used with variables (constant), methods (cannot be overridden), and classes (cannot be inherited).

Q25: What is the difference between break and continue?

A: break exits a loop entirely; continue skips the current iteration and proceeds to the next.

Q26: What is exception handling in Java?

A: It is a mechanism to handle runtime errors using try, catch, throw, throws, and finally.

Q27: What is the difference between checked and unchecked exceptions?

A: Checked exceptions are checked at compile time (IOException), unchecked at runtime (NullPointerException).

Q28: What is a try-with-resources statement?

A: It's used to automatically close resources like files or sockets that implement AutoCloseable.

Q29: What is the difference between ArrayList and LinkedList?

A: ArrayList is faster for indexing; LinkedList is better for insert/delete operations.

Q30: What is a Map in Java?

A: A Map is an object that maps keys to values. It cannot contain duplicate keys.

Q31: What are the different types of loops in Java?

A: for, while, and do-while loops are available for iteration.

Q32: What is a constructor overloading?

A: Constructor overloading means having more than one constructor with different parameters in a class.

Q33: What is a String in Java?

A: A String is an object that represents a sequence of characters. Strings are immutable in Java.

Q34: What is the difference between String, StringBuffer, and StringBuilder?

A: String is immutable. StringBuffer is thread-safe and mutable. StringBuilder is mutable but not thread-safe.

Q35: What is the use of ‘this’ keyword?

A: ‘this’ refers to the current object inside a method or constructor.

Q36: What is the difference between equals() and hashCode()?

A: equals() checks logical equality, hashCode() returns an integer for hashing in collections like HashMap.

Q37: What is an Enum in Java?

A: Enum is a special Java type used to define collections of constants.

Q38: What is mithreading?

A: Multithreading allows concurrent execution of two or more threads for maximum CPU utilization.

Q39: How do you create a thread in Java?

A: By extending the Thread class or implementing the Runnable interface.

Q40: What is synchronization?

A: Synchronization is used to control access to shared resources by multiple threads to avoid data inconsistency.

📌 FAQ: Java Interview Preparation

Q1: Are these Java questions suitable for freshers?

Yes! This collection includes beginner to advanced-level Java questions commonly asked in campus placements and MNC interviews.

Q2: Do you provide answers for all 2000 questions?

Yes, every question is answered clearly. Download the full PDF for all content.

Q3: Can I use this for college viva or practicals?

Absolutely. These questions help with viva, assignments, and project evaluations.

📚 Related Java Course:

👉 Learn Java Free: Complete 14-Chapter Course (Beginner to Advanced)

Written by: Op Verma | Assistant Professor, SMCET Phagi

📅 Updated: July 2025

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