1. What is JVM? 2. Difference between `==` and `equals()`? 3. What is inheritance? 4. What is method overloading? 5. What is multithreading? 6. What is polymorphism? 7. Difference between Array and ArrayList? 8. What is encapsulation? 9. Difference between HashMap and Hashtable? 10. What is constructor? 11. Difference between interface and abstract class? 12. What is exception handling? 13. Difference between String and StringBuilder? 14. What is method overriding? 15. What is Collection Framework?