Core Java - Interview Questions

1. What is immutable class?

2. Differentiate LinkedHashMap, HashMap, SortedHashMap,concurrentHashMap,TreeHashMap

3. What is Marker Interface?

4. What is the use of volatile Keyword?

5. Methods in Object class

6. Differentiate Instance, Global, static variables

7. Heap Memory vs Stack Memory

8. What Happens when duplicate Key inserted in HashMap?

9. What Happens when try to print a key which does not exist in HashMap?

10. How to make a class as Singleton?

11. When to use Abstract class vs Interface?

12. How many copies of static variable will be there in the memory?

13. JVM vs JRE

14. What are the differences between Heap and Stack Memory in Java?