Java Interview Questions and Answers
This page contains important Java Interview Questions and Answers for beginners and freshers.
These questions are commonly asked in technical interviews.
1. What is Java?
Java is a high-level, object-oriented, platform-independent programming language used to build web, desktop, and enterprise applications.
2. What is JVM?
JVM (Java Virtual Machine) is a virtual machine that runs Java bytecode and makes Java platform independent.
3. What is the difference between JDK, JRE, and JVM?
- JDK – Java Development Kit (used to develop programs)
- JRE – Java Runtime Environment (used to run programs)
- JVM – Executes Java bytecode
4. What is OOP?
OOP (Object-Oriented Programming) is a programming concept based on objects and classes.
5. What are the main OOP principles?
- Encapsulation
- Inheritance
- Polymorphism
- Abstraction
6. What is the difference between == and equals()?
- == compares memory reference.
- equals() compares object values.
7. What is Exception Handling?
Exception Handling is a mechanism to handle runtime errors using try, catch, and finally blocks.
8. What is the difference between Checked and Unchecked Exceptions?
- Checked exceptions are checked at compile time.
- Unchecked exceptions occur at runtime.
9. What is the difference between Array and ArrayList?
- Array has fixed size.
- ArrayList has dynamic size.
- Array can store primitives.
- ArrayList stores objects only.
10. What is Multithreading?
Multithreading allows multiple threads to run simultaneously in a program.
11. What is the use of final keyword?
- final variable – cannot change value
- final method – cannot override
- final class – cannot inherit
12. What is Constructor?
A constructor is a special method used to initialize objects. It has the same name as the class.
class Student {
Student() {
System.out.println("Constructor called");
}
}
13. What is the difference between interface and abstract class?
- Interface supports multiple inheritance.
- Abstract class can have both abstract and non-abstract methods.
14. What is Spring Boot?
Spring Boot is a Java framework used to build production-ready web applications quickly.
15. What is JDBC?
JDBC (Java Database Connectivity) is used to connect Java applications with databases.
Tips for Java Interview
- Understand OOP concepts clearly.
- Practice coding daily.
- Know basic Java syntax.
- Be confident while explaining answers.
- Prepare small projects.
Conclusion
These Java Interview Questions will help you prepare for technical interviews.
Practice coding and revise concepts regularly to crack interviews.