15 Core Java Questions Interview Questions(1-3 Yrs)

1. What are the 4 main OOPs concepts?
2. What is the difference between Overloading and Overriding?
3. Explain the different types of inheritance in java?
4. What is the differance between abstract class and interface?
5. Differance between finally,final and finalize?
6. Explain the Garbage Collection in java?
7. What are the methods in Object class?
8. Explain the collection hierarchy?
9. Differnce between List and Set?
10. Difference between HashTable and HashSet?
11. How hashmap internally works
12. Difference between JDK,JRE and JVM?
13. What is Stack and Heap memory?
14. Why string is immutale in Java?
15. How can we create a immutable class?