30 Toughest Java and Spring Interview Questions with One-Line Answers

For experienced developers, interviews often include challenging questions that test deep understanding. This blog covers 30 tough theory-based Java and Spring questions to help you excel in your next interview.

Advanced Java Questions

1. What is a ClassLoader in Java?
   Answer: A ClassLoader loads Java classes into the JVM at runtime.
2. What is the difference between stack and heap memory?
   Answer: Stack memory stores method calls and local variables, while heap memory stores objects.
3. What is the significance of synchronized blocks?
   Answer: They ensure thread-safe access to critical sections of code.
4. How does Java achieve platform independence?
   Answer: Java compiles source code into bytecode, which is executed by the JVM on any platform.
5. What is the difference between HashMap and ConcurrentHashMap?
   Answer: HashMap is not thread-safe, while ConcurrentHashMap allows concurrent access with locks.
6. What is the difference between shallow and deep cloning in Java?
   Answer: Shallow cloning copies the object but not its references, while deep cloning copies the object and its references.
7. What is Java Reflection, and why is it used?
   Answer: Reflection…