*Intermediate Java Interview Questions with Answers– Part 5* *21. What is a static block in Java and when is it executed?* A static block is used to initialize static variables. It runs once when the class is first loaded into memory. *Example:* class MyClass { static int value; static { value = 10; System.out.println("Static block executed"); } } *22. Can a class extend multiple classes in Java? Why not?* No, Java does not support multiple inheritance with classes to avoid ambiguity. A class can only extend one class, but it can implement multiple interfaces. *23. What is marker interface in Java?* A marker interface is an interface with no methods or fields. It's used to convey metadata or behavior to the JVM or frameworks. *Example:* Serializable, Cloneable are marker interfaces. *24. What is the difference between wait(), sleep(), and join() in Java?* wait() – releases the lock and waits to be notified. Used in inter-thread communication. sleep() – pauses the thread for a specific time but does not release the lock. join() – makes the current thread wait until another thread finishes execution. *25. What is the volatile keyword in Java?* The volatile keyword ensures visibility of changes to variables across threads. It prevents thread caching of variables and always reads from the main memory. *Example:* volatile boolean running = true; *React ❤️ for more*