JVM, Memory Management & Exception Handling

Posted on by Rahul Mittal

MCQs

Q1. Which JVM memory area stores objects?

A. Stack

B. Heap

C. Method Area

D. Program Counter

Q2. What is Garbage Collection?

A. Memory Allocation

B. Memory Cleanup of Unused Objects

C. Object Creation

D. Stack Cleanup

Q3. Which exception is unchecked?

A. SQLException

B. IOException

C. ClassNotFoundException

D. NullPointerException

Q4. Which keyword is used to explicitly throw an exception?

A. throws

B. throw

C. catch

D. finally

Q5. What is the purpose of finally block?

A. Catch exceptions

B. Create exceptions

C. Execute cleanup code

D. Handle JVM shutdown

Q6. Can a finally block execute if return is present in try?

A. No

B. Yes

Q7. What causes OutOfMemoryError?

A. Stack Overflow

B. Heap Exhaustion

C. Database Failure

D. Network Timeout

Q8. Which memory area stores method calls?

A. Heap

B. Stack

C. Method Area

D. Native Heap

Programming Exercise

Problem Statement

A number is called an Armstrong Number if the sum of cubes of its digits equals the original number.

Example:

153 = 1³ + 5³ + 3³

Write a Java program to check whether a number is Armstrong or not.

Input:

153

Output:

Armstrong Number

SQL Question

Employee

emp_id | emp_name | salary
1      | John     | 10000
2      | Sam      | 20000
3      | Alice    | 30000
4      | Bob      | 15000

Find employees earning more than average salary.

Architecture Question

Explain Heap vs Stack memory and common memory-related issues in Java applications.

ANSWERS – SET 6

MCQs

1-B
2-B
3-D
4-B
5-C
6-B
7-B
8-B

Explanations

  • Heap stores objects.
  • GC reclaims unreachable objects.
  • NullPointerException is unchecked.
  • throw throws exception; throws declares exception.
  • finally is used for resource cleanup.
  • finally executes even if return exists.
  • OutOfMemoryError usually indicates heap exhaustion.
  • Stack stores method calls and local variables.

Programming Solution

public class Armstrong {

    public static void main(String[] args) {

        int num = 153;
        int temp = num;
        int sum = 0;

        while(temp > 0) {
            int digit = temp % 10;
            sum += digit * digit * digit;
            temp /= 10;
        }

        if(sum == num)
            System.out.println("Armstrong Number");
        else
            System.out.println("Not Armstrong Number");
    }
}

Complexity:

Time: O(D)

Space: O(1)

Where D = Number of digits.

SQL

SELECT *
FROM Employee
WHERE salary >
(
    SELECT AVG(salary)
    FROM Employee
);

Architecture Answer

Heap:

  • Stores objects
  • Shared across threads

Stack:

  • Stores local variables
  • Thread specific

Common Issues:

  • Memory Leak
  • OutOfMemoryError
  • StackOverflowError

REVIEW SHEET – SET 6

AreaScore
JVM
Programming
SQL
Architecture
Total

INTERVIEW SET 7 – Collections Framework Deep Dive

MCQs

Q1. Which collection stores unique elements?

A. List

B. ArrayList

C. Set

D. Vector

Q2. Which collection provides O(1) average lookup?

A. TreeMap

B. HashMap

C. LinkedList

D. TreeSet

Q3. TreeMap internally uses?

A. Hash Table

B. Array

C. Red Black Tree

D. Linked List

Q4. Which collection maintains insertion order?

A. HashMap

B. TreeMap

C. LinkedHashMap

D. Hashtable

Q5. Hashtable allows null keys?

A. Yes

B. No

Q6. ConcurrentHashMap is primarily used for?

A. Sorting

B. Thread Safety

C. Serialization

D. Reflection

Q7. Which interface is parent of List?

A. Map

B. Collection

C. Iterable

D. Queue

Q8. Which collection is best for FIFO?

A. Stack

B. PriorityQueue

C. Queue

D. TreeSet

Programming Exercise

Count duplicate words in a sentence.

Input:

java spring java boot spring java

Output:

java=3
spring=2
boot=1

SQL Question

Employee

emp_id | emp_name | dept_id
1      | John     | 10
2      | Sam      | 20
3      | Alice    | 10
4      | Bob      | 10

Find departments having more than 2 employees.

Architecture Question

HashMap vs ConcurrentHashMap. Explain use cases.

ANSWERS – SET 7

MCQs:

1-C
2-B
3-C
4-C
5-B
6-B
7-B
8-C

Programming

String input =
    "java spring java boot spring java";

String[] words = input.split(" ");

Map<String,Integer> map =
        new HashMap<>();

for(String word : words) {
    map.put(word,
        map.getOrDefault(word,0)+1);
}

Time: O(N)

Space: O(N)

SQL

SELECT dept_id,
       COUNT(*)
FROM Employee
GROUP BY dept_id
HAVING COUNT(*) > 2;

Architecture

HashMap:

  • Not Thread Safe
  • Faster

ConcurrentHashMap:

  • Thread Safe
  • Segment/Bucket level locking
  • Suitable for concurrent applications

REVIEW SHEET – SET 7

AreaScore
Collections
Programming
SQL
Architecture
Total

INTERVIEW SET 8 – Java 8 Streams & Functional Programming

MCQs

Q1. What is a Functional Interface?

A. Multiple Abstract Methods

B. One Abstract Method

C. No Methods

D. Only Default Methods

Q2. Which annotation marks Functional Interface?

A. @FunctionalInterface

B. @Override

C. @Component

D. @Bean

Q3. Which stream operation transforms data?

A. filter()

B. count()

C. map()

D. collect()

Q4. Which operation removes elements?

A. map()

B. collect()

C. filter()

D. reduce()

Q5. reduce() is used for?

A. Aggregation

B. Filtering

C. Sorting

D. Mapping

Q6. Which operation is terminal?

A. filter()

B. map()

C. sorted()

D. collect()

Q7. What is Method Reference?

A. Lambda Shortcut

B. Interface

C. Collection

D. Annotation

Q8. Optional prevents?

A. Deadlocks

B. Memory Leaks

C. NullPointerException

D. Serialization Errors

Programming Exercise

Using Java 8 Streams:

Find all even numbers from a list and return their squares.

Input:

1,2,3,4,5,6

Output:

4,16,36

SQL Question

Orders

order_id | customer_id | amount
101      | 1           | 500
102      | 1           | 700
103      | 2           | 300
104      | 2           | 900

Find total amount spent by each customer.

Architecture Question

Advantages and disadvantages of Stream API.

ANSWERS – SET 8

MCQs:

1-B
2-A
3-C
4-C
5-A
6-D
7-A
8-C

Programming

List<Integer> result =
numbers.stream()
       .filter(n -> n % 2 == 0)
       .map(n -> n * n)
       .collect(Collectors.toList());

Time: O(N)

Space: O(N)

SQL

SELECT customer_id,
       SUM(amount)
FROM Orders
GROUP BY customer_id;

Architecture

Advantages:

  • Readable
  • Functional style
  • Parallel processing

Disadvantages:

  • Debugging harder
  • May not suit all use cases

REVIEW SHEET – SET 8

AreaScore
Java 8
Programming
SQL
Architecture
Total

INTERVIEW SET 9 – Spring Boot & Microservices

MCQs

Q1. What is IOC?

A. Inversion of Control

B. Internal Object Control

C. Input Output Controller

D. Internet Object Controller

Q2. Which annotation injects dependency?

A. @Bean

B. @Autowired

C. @Primary

D. @Value

Q3. Which annotation creates REST APIs?

A. @Controller

B. @Repository

C. @RestController

D. @Service

Q4. Default bean scope?

A. Prototype

B. Singleton

C. Session

D. Request

Q5. What is API Gateway used for?

A. Database Access

B. Service Entry Point

C. Logging

D. Caching

Q6. Which protocol is commonly used between microservices?

A. SMTP

B. FTP

C. HTTP/REST

D. POP3

Q7. What is Service Discovery?

A. Finding Databases

B. Locating Microservices

C. Logging Services

D. Security Service

Q8. Spring Boot Actuator is used for?

A. Monitoring

B. ORM

C. Security

D. Scheduling

Programming Exercise

Given a list of Employee objects:

Return employee names sorted by salary descending.

SQL Question

Employee

emp_id | emp_name | dept_id | salary

Find highest paid employee in each department.

Architecture Question

Explain Microservice Architecture and common challenges.

ANSWERS – SET 9

MCQs:

1-A
2-B
3-C
4-B
5-B
6-C
7-B
8-A

Programming

employees.stream()
         .sorted(
             Comparator.comparing(
                 Employee::getSalary)
             .reversed())
         .map(Employee::getName)
         .collect(Collectors.toList());

SQL

SELECT dept_id,
       MAX(salary)
FROM Employee
GROUP BY dept_id;

Architecture

Challenges:

  • Distributed Transactions
  • Service Discovery
  • Monitoring
  • Logging
  • Fault Tolerance

Advantages:

  • Independent Deployment
  • Independent Scaling

REVIEW SHEET – SET 9

AreaScore
Spring
Programming
SQL
Architecture
Total

INTERVIEW SET 10 – Design Patterns & System Design

MCQs

Q1. Factory Pattern is used for?

A. Object Creation

B. Behavior Selection

C. Event Handling

D. Caching

Q2. Strategy Pattern is used for?

A. Object Creation

B. Encapsulating Algorithms

C. Logging

D. Serialization

Q3. Singleton ensures?

A. Multiple Instances

B. Single Instance

C. Multiple Threads

D. Caching

Q4. Which SOLID principle does Strategy support?

A. OCP

B. SRP

C. ISP

D. LSP

Q5. Observer Pattern is used in?

A. Event Notification

B. Object Creation

C. Logging

D. Serialization

Q6. Which pattern is heavily used by Spring?

A. Singleton

B. Factory

C. Dependency Injection

D. All of the Above

Q7. Horizontal scaling means?

A. Bigger Server

B. More Servers

C. Faster CPU

D. Bigger JVM

Q8. Load Balancer is used for?

A. Security

B. Request Distribution

C. Logging

D. Database Access

Programming Exercise

Print Fibonacci Series up to N terms.

Input:

10

Output:

0 1 1 2 3 5 8 13 21 34

SQL Question

Employee

emp_id | emp_name | manager_id
1      | John     | NULL
2      | Sam      | 1
3      | Alice    | 1
4      | Bob      | 2

Display employee name along with manager name.

Architecture Question

Design a Notification System supporting:

  • Email
  • SMS
  • Push Notifications

Discuss design patterns and scalability considerations.

ANSWERS – SET 10

MCQs:

1-A
2-B
3-B
4-A
5-A
6-D
7-B
8-B

Programming

int a = 0;
int b = 1;

for(int i=1;i<=10;i++) {

    System.out.print(a + " ");

    int c = a + b;
    a = b;
    b = c;
}

Time: O(N)

Space: O(1)

SQL

SELECT e.emp_name,
       m.emp_name AS manager_name
FROM Employee e
LEFT JOIN Employee m
ON e.manager_id = m.emp_id;

Architecture

Design Patterns:

  • Strategy Pattern
  • Factory Pattern

Scalability:

  • Queue based delivery
  • Retry mechanism
  • DLQ
  • Horizontal scaling
  • Notification status tracking

FINAL INTERVIEW EVALUATION GUIDE

ScoreRecommendation
90 – 100Strong Hire
80 – 89Hire
70 – 79Conditional Hire
60 – 69Borderline
Below 60Reject

Skills Matrix

SkillWeight
Core JavaHigh
OOPHigh
CollectionsHigh
Java 8High
Spring BootHigh
SQLMedium
Design PatternsMedium
ArchitectureHigh
Problem SolvingHigh

Strong Hire Indicators

  • Explains JVM memory confidently
  • Understands Java 8 beyond syntax
  • Can write joins and group by queries
  • Knows Spring IOC and DI clearly
  • Uses appropriate design patterns
  • Explains time and space complexity
  • Demonstrates architecture thinking

Red Flags

  • Cannot differentiate HashMap and ConcurrentHashMap
  • Weak understanding of Streams
  • No knowledge of Spring Bean lifecycle
  • Unable to write JOIN queries
  • Memorized design patterns without use cases
  • Cannot explain complexity of solutions

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