Most frequently asked interview Questions

In this article, we will cover some of the interview questions asked in campus placement interviews.These are most frequently asked interview questions. 

I will keep updating questions in this post, so keep visiting :) . 
If you have any questions or wants to submit your questions comment below.

Sources For Preparation:

• Geeksforgeeks for all concepts
• Indiabix, http://pariksha.co/ for aptitude
• BenchResources for java collections and diffrences
• Hackerrank, hackerearth for coding

OOP INTERVIEW QUESTIONS

1. What is Object & Class.Give real time examples.
2. Why OOP? Other programming Paradigms(You should at least know names e.g. Procedural, Functional Programming)
3. What is Abstraction, Encapsulation, Data hiding. Examples
4. Inheritance, Why it is important?( Reusability)
5. Polymorphism, Runtime and compile time (Explain it with programming example).
6. Difference Between Abstract class and Interface. When to use abstract class and when to use Interface.
7. Which OOP concepts you have used while implementing your project.
8. Aggregation and composition. Real life examples

JAVA INTERVIEW QUESTIONS:

1. Why java is not a purely Object-Oriented Language?
2. How is Java platform independent?
3. Abstraction, Interface, Runtime polymorphism in java
4. Method overloading vs Overriding
5. Why main method is static?
6. Static, final, finalize(), Access modifiers, super, finally
7. Object Class, Its methods (Every class directly or indirectly inherits object class)
8. Static block , when it is executed
9. Why Java does’nt support Multiple Inheritance – The Diamond Problem
10. https://www.geeksforgeeks.org/g-fact-91/
11. C++ vs java
12. Exception handling, Types of Exceptions (checked unchecked, Examples), finally block. When finally block will be skipped?
13. Most important. If interview asks which is your favourite language. Mention specific version. E.g. JAVA 1.8 You should know features of java 1.8 (It will be a plus point)
14. JAVA 1.8 features : Lambda Function, Collection foreach method, Streams, Time API, interface can contain default methods.See some examples online.
15. Multithreading, Different methods to implement multithreading? When to use which method, Threading Lifecycle
16. Synchronize keyword
17. Garbage Collection
18. How to make object eligible for garbage collection in Java?
19. Mark-and-Sweep   Its very important you should know how it works internally
20. Wrapper classes ,Primitive Wrapper Classes are Immutable in Java
21. Collections, its hierarchy of classes and interfaces
22. HashMap, Hashset,LinkedHashset, TreeSet ArrayList, LinkedList are important
23. http://www.benchresources.net/java/collection-framework/  ALL differences are on this site. You should remember at least 3 differences between each pair.
24. Search when to you use which collection, It will help you to solve programming questions also.
25. Working of HashMap
26. Hashset vs Hashmap, Hashmap vs Hashtable, ArrayList vs LinkedList,Treeset vs Hashset
27. How to make HashMap Synchronized?
28. Immutable class? Why is String Class immutable? How to make immutable class?
29. https://www.geeksforgeeks.org/g-fact-27-string-vs-stringbuilder-vs-stringbuffer/
30. JAVA JDBC Code(Some interviewers asks to write this code snippet)
31. https://www.geeksforgeeks.org/biginteger-class-in-java/  Its Imopertant for coding. (If you have to find factorial of large number)

P.S. While Studying any concept don’t just recite its features and definition. Always prepare for  WHY this is required?

DBMS INTERVIEW QUESTIONS:

1. DBMS INTERVIEW QUESTIONS SET 1
2. DBMS INTERVIEW QUESTIONS SET 2
3. Difference between RDBMS and NOSQL, examples of DBs
4. Primary key vs Unique
5. Foreign Key, other constrains
6. Find 2nd Highest salary of employees

   SELECT max(salary) FROM EMPLOYEES WHERE salary IN (SELECT salary FROM EMPLOYEEs MINUS SELECT max(salary)
   FROM EMPLOYEES);

   OR

   SELECT max(salary) FROM EMPLOYEES WHERE 
   salary <> (SELECT max(salary) FROM EMPLOYEES);

7. Why we cannot use WHERE clause with aggregate functions like HAVING ?
8. Name the student who has secured third highest marks using sub queries.

   SELECT Emp1.Name
   FROM Employee Emp1
   WHERE 2 = (SELECT COUNT(DISTINCT(Emp2.Salary))
              FROM Employee Emp2
              WHERE Emp2.Salary > Emp1.Salary
             )

9. JOINS, SUB-QUERIES examples
10. Database schema of your project
11. Index , types why it is used?
12. When you will use relational DB and NOSql Db?

I will update remaining questions in some days. Keep Visiting :) .