Java interview questions with answers 👇👇

1. What is Java?
Java is a high-level, object-oriented programming language developed by Sun Microsystems. It is platform-independent, meaning it can run on any device with the Java Virtual Machine (JVM) installed.

2. What is the difference between JDK, JRE, and JVM?
- JDK (Java Development Kit): It is a software development kit used for developing Java applications. It includes the JRE and development tools such as compilers and debuggers.
- JRE (Java Runtime Environment): It is an environment in which Java programs are executed. It includes the JVM and libraries necessary to run Java applications.
- JVM (Java Virtual Machine): It is an abstract machine that provides a runtime environment in which Java bytecode can be executed.

3. What are the main features of Java?
- Object-oriented: Java supports the concept of classes and objects.
- Platform-independent: Java programs can run on any device with a JVM installed.
- Simple: Java has a simple syntax and easy-to-use APIs.
- Secure: Java provides a secure runtime environment with features like bytecode verification and security manager.
- Multithreaded: Java supports multithreading, allowing multiple tasks to run concurrently.

4. What is the difference between an interface and an abstract class in Java?
- Interface: An interface in Java is a collection of abstract methods and constants. A class can implement multiple interfaces but cannot extend multiple classes.
- Abstract class: An abstract class in Java is a class that cannot be instantiated and may contain both abstract and concrete methods. A class can extend only one abstract class.

5. What is the difference between == and equals() method in Java?
- ==: The == operator in Java compares the memory addresses of two objects.
- equals(): The equals() method in Java compares the content of two objects. It is used to compare the values of objects.

6. What is a constructor in Java?
A constructor in Java is a special method that is used to initialize an object. It has the same name as the class and does not have a return type.

7. What is the difference between static and non-static methods in Java?
- Static method: A static method in Java belongs to the class rather than an instance of the class. It can be called using the class name.
- Non-static method: A non-static method in Java belongs to an instance of the class and can only be called using an object of the class.

8. What is the difference between checked and unchecked exceptions in Java?
- Checked exception: Checked exceptions are checked at compile time and must be handled by the programmer using try-catch or throws keyword.
- Unchecked exception: Unchecked exceptions are not checked at compile time and do not need to be handled by the programmer.

9. What is method overloading in Java?
Method overloading in Java is a feature that allows a class to have multiple methods with the same name but different parameters. The compiler determines which method to call based on the number and type of arguments passed.

10. What is method overriding in Java?
Method overriding in Java is a feature that allows a subclass to provide a specific implementation of a method that is already defined in its superclass. The overridden method must have the same name, return type, and parameters as the method in the superclass.

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