---
type: archive
area: archive
status: archived
date: 2026-05-03
created: 2026-05-03
updated: 1980-01-01
tags:
  - archive
---
Core Java Concepts:  
1. What is the difference between JDK and JRE?  
2. Why is Java platform-independent?  
3. What is the difference between an abstract class and an interface?  
4. What is the difference between final, finally, and finalize?  
5. What is the difference between stack and heap memory?  
6. What is method overloading vs. method overriding?  
7. What’s the difference between a private and protected modifier?  
8. What is constructor overloading in Java?  
9. How is the super keyword used in Java?  
10. What is the difference between static methods, variables, and classes?  
11. What is System.out.println in Java?  
12. What part of memory (Stack or Heap) is cleaned during garbage collection?  
  
Object-Oriented Programming:  
1. What Object-Oriented features are supported by Java?  
2. What are the different access specifiers in Java?  
3. What’s the difference between composition and inheritance?  
4. What is the purpose of an abstract class?  
5. What’s the difference between a constructor and a method?  
6. What is the diamond problem in Java, and how is it resolved?  
7. How do local and instance variables differ?  
8. What is a Marker interface in Java?  
  
Data Structures and Algorithms:  
1. Why are strings immutable in Java?  
2. What’s the difference between creating a String using new() and as a literal?  
3. What is the Collections framework?  
4. How do ArrayList and LinkedList differ?  
5. What is the difference between a HashMap and a TreeMap?  
6. How do HashSet and TreeSet differ?  
7. What’s the difference between an Iterator and a ListIterator?  
8. What is the purpose of the Comparable interface?  
9. What is the java.util.concurrent package for?  
  
Exception Handling:  
1. What is an exception in Java?  
2. How does exception propagation work?  
3. What’s the difference between checked and unchecked exceptions?  
4. What is the use of the try-catch block in Java?  
5. How do throw and throws differ?  
6. What is the use of the finally block?  
7. What’s the base class of all exception classes?  
  
Multithreading:  
1. What is a thread, and what are its stages in Java?  
2. How do threads differ from processes?  
3. What are the different types of thread priorities in Java?  
4. What is context switching in Java?  
5. What’s the difference between user threads and Daemon threads?  
6. What is synchronization in Java?  
7. What is a deadlock in Java?  
8. How are the wait() and notify() methods used?  
9. What’s the difference between synchronized and volatile in Java?  
10. What’s the purpose of the sleep() method?  
11. How do wait() and sleep() differ?  
12. What’s the difference between notify() and notifyAll()?  
  
Java Enterprise Edition (Java EE):  
1. What is Java EE?  
2. How do Servlets and JSP differ?  
3. What is the purpose of the Java Persistence API (JPA)?  
4. What’s the difference between stateful and stateless session beans?