Frequently asked questions for Java Developer Position from a fresher

Java Based:

1. OOPs concepts ( mostly polymorphism and difference between encapsulation and abstraction)
2. Difference between abstract class and interface.
3. Difference between == and .equals() functions.
4. What is Hash Map ?
5. What is Hash Table ?
6. Types of Exceptions.
7. Difference between Exceptions and Errors.
8. Difference between throw, throws and throwable.
9. Difference between final, finalize and finally.
10. What is class?
11. What is an object?
12. Difference between class and object.
13. Method overloading.
14. Method overriding.
15. What is a thread?
16. Different ways to create threads.
17. Difference between C and Java.
18. Difference between CPP and Java.
19. File handling in java.

Algorithms:

1. Binary Search
2. Quick Sort (Complexity and logic )
3. Merge Sort (Complexity and logic )
4. Difference between Merge sort, Quick sort
5. Which one is better Merge sort or Quick sort and why ?
6. BFS
7. DFS

Data Structures:

1. What is a binary tree?
2. What is binary search tree?
3. What is linked list and its types.
4. Implement stack/queue using linked list.
5. Memory management (Heap and stack )
6. AVL tree
7. Difference between array and linked list.
8. Reverse a linked list.
9. Find middle element of a linked list.
10. How to Detect loop in a linked list?
11. Top view / Left view / Right view / Diagonal view of binary tree
12. Right rotate a matrix
13. Check if a binary tree is sub tree of another binary tree.

Operating System:

1. Difference between process and thread.
2. What is dead lock?
3. Critical Section Problem
4. What is Thrashing ?
5. Paging.
6. Page Fault.

DBMS:

1. Difference between Primary key and Candidate key.
2. What are Joins and types of Joins.
3. Find second highest salary from Employee table.
4. ACID Properties.

Other questions:

1. Reverse a string.
2. Find maximum occurring character/word in a given string.
3. Recursively check if a given string is a palindrome.