Java coding interview questions
1. Reverse a String:
Write a Java program to reverse a given string.
2. Find the Largest Element in an Array:
Find and print the largest element in an array.
3. Check for Palindrome:
Determine if a given string is a palindrome (reads the same backward as forward).
4. Factorial Calculation:
Write a function to calculate the factorial of a number.
5. Fibonacci Series:
Generate the first n numbers in the Fibonacci sequence.
6. Check for Prime Number:
Write a program to check if a given number is prime.
7. String Anagrams:
Determine if two strings are anagrams of each other.
8. Array Sorting:
Implement sorting algorithms like bubble sort, merge sort, or quicksort.
9. Binary Search:
Implement a binary search algorithm to find an element in a sorted array.
10. Duplicate Elements in an Array:
Find and print duplicate elements in an array.
11. Linked List Reversal:
Reverse a singly-linked list.
12. Matrix Operations:
Perform matrix operations like addition, multiplication, or transpose.
13. Implement a Stack:
Create a stack data structure and implement basic operations (push, pop).
14. Implement a Queue:
Create a queue data structure and implement basic operations (enqueue, dequeue).
15. Inheritance and Polymorphism:
Implement a class hierarchy with inheritance and demonstrate polymorphism.
16. Exception Handling:
Write code that demonstrates the use of try-catch blocks to handle exceptions.
17. File I/O:
Read from and write to a file using Java's file I/O capabilities.
18. Multithreading:
Create a simple multithreaded program and demonstrate thread synchronization.
19. Lambda Expressions:
Use lambda expressions to implement functional interfaces.
20. Recursive Algorithms:
Solve a problem using recursion, such as computing the factorial or Fibonacci sequence.
Best Java Resources: https://whatsapp.com/channel/0029VamdH5mHAdNMHMSBwg1s
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1. Reverse a String:
Write a Java program to reverse a given string.
2. Find the Largest Element in an Array:
Find and print the largest element in an array.
3. Check for Palindrome:
Determine if a given string is a palindrome (reads the same backward as forward).
4. Factorial Calculation:
Write a function to calculate the factorial of a number.
5. Fibonacci Series:
Generate the first n numbers in the Fibonacci sequence.
6. Check for Prime Number:
Write a program to check if a given number is prime.
7. String Anagrams:
Determine if two strings are anagrams of each other.
8. Array Sorting:
Implement sorting algorithms like bubble sort, merge sort, or quicksort.
9. Binary Search:
Implement a binary search algorithm to find an element in a sorted array.
10. Duplicate Elements in an Array:
Find and print duplicate elements in an array.
11. Linked List Reversal:
Reverse a singly-linked list.
12. Matrix Operations:
Perform matrix operations like addition, multiplication, or transpose.
13. Implement a Stack:
Create a stack data structure and implement basic operations (push, pop).
14. Implement a Queue:
Create a queue data structure and implement basic operations (enqueue, dequeue).
15. Inheritance and Polymorphism:
Implement a class hierarchy with inheritance and demonstrate polymorphism.
16. Exception Handling:
Write code that demonstrates the use of try-catch blocks to handle exceptions.
17. File I/O:
Read from and write to a file using Java's file I/O capabilities.
18. Multithreading:
Create a simple multithreaded program and demonstrate thread synchronization.
19. Lambda Expressions:
Use lambda expressions to implement functional interfaces.
20. Recursive Algorithms:
Solve a problem using recursion, such as computing the factorial or Fibonacci sequence.
Best Java Resources: https://whatsapp.com/channel/0029VamdH5mHAdNMHMSBwg1s
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Commonly asked System Design CONCEPT BASED interview topics -
1. Horizontal vs Vertical Partitioning:
Vertical partitioning splits tables by columns, often separating different features. Horizontal partitioning splits tables by rows, distributing data across multiple servers. Vertical organizes data logically, while horizontal improves scalability + performance.
2. Apache Kafka:
Kafka is a distributed streaming platform using a publish-subscribe model. It's fast due to the sequential disk I/O, zero-copy principle, and efficient batching of messages.
3. Rate Limiter:
A rate limiter controls the rate of requests a client can make to a service. It prevents overload and ensures fair resource usage.
4. JWT vs OAuth vs SAML:
JWT is a compact, self-contained token for secure information transmission. OAuth is an authorization framework for delegated access. SAML is an XML-based standard for exchanging authentication and authorization data.
5. Single Sign-On (SSO):
SSO allows users to access multiple applications with one set of credentials. It typically uses a central authentication server and protocols like SAML/OAuth.
6. Microservices vs Monolithic Architecture:
Microservices architecture breaks an application into small, independent services. Monolithic architecture is a single, tightly-coupled unit. Microservices offer scalability while monoliths are simpler to develop + deploy.
7. Reverse Proxy vs Forward Proxy:
A reverse proxy sits in front of web servers, forwarding client requests to backend servers. A forward proxy sits in front of clients, forwarding their requests to the internet. Reverse proxies are used for load balancing and security, while forward proxies are used for anonymity and filtering.
8. CAP Theorem:
The CAP theorem states that a distributed system can only provide two of three guarantees: Consistency, Availability, and Partition tolerance. In practice, partition tolerance is necessary, so systems must choose between consistency and availability during network partitions.
10. Efficient Caching Strategy:
Implement multi-level caching (browser, CDN, application server, database). Use appropriate cache invalidation strategies (TTL, event-based). Consider cache coherence for distributed systems.
Best DSA RESOURCES: https://topmate.io/coding/886874
All the best 👍👍
1. Horizontal vs Vertical Partitioning:
Vertical partitioning splits tables by columns, often separating different features. Horizontal partitioning splits tables by rows, distributing data across multiple servers. Vertical organizes data logically, while horizontal improves scalability + performance.
2. Apache Kafka:
Kafka is a distributed streaming platform using a publish-subscribe model. It's fast due to the sequential disk I/O, zero-copy principle, and efficient batching of messages.
3. Rate Limiter:
A rate limiter controls the rate of requests a client can make to a service. It prevents overload and ensures fair resource usage.
4. JWT vs OAuth vs SAML:
JWT is a compact, self-contained token for secure information transmission. OAuth is an authorization framework for delegated access. SAML is an XML-based standard for exchanging authentication and authorization data.
5. Single Sign-On (SSO):
SSO allows users to access multiple applications with one set of credentials. It typically uses a central authentication server and protocols like SAML/OAuth.
6. Microservices vs Monolithic Architecture:
Microservices architecture breaks an application into small, independent services. Monolithic architecture is a single, tightly-coupled unit. Microservices offer scalability while monoliths are simpler to develop + deploy.
7. Reverse Proxy vs Forward Proxy:
A reverse proxy sits in front of web servers, forwarding client requests to backend servers. A forward proxy sits in front of clients, forwarding their requests to the internet. Reverse proxies are used for load balancing and security, while forward proxies are used for anonymity and filtering.
8. CAP Theorem:
The CAP theorem states that a distributed system can only provide two of three guarantees: Consistency, Availability, and Partition tolerance. In practice, partition tolerance is necessary, so systems must choose between consistency and availability during network partitions.
10. Efficient Caching Strategy:
Implement multi-level caching (browser, CDN, application server, database). Use appropriate cache invalidation strategies (TTL, event-based). Consider cache coherence for distributed systems.
Best DSA RESOURCES: https://topmate.io/coding/886874
All the best 👍👍
❤5
Template to ask for referrals
(For freshers)
👇👇
(For freshers)
👇👇
Hi [Name],
I hope this message finds you well.
My name is [Your Name], and I recently graduated with a degree in [Your Degree] from [Your University]. I am passionate about data analytics and have developed a strong foundation through my coursework and practical projects.
I am currently seeking opportunities to start my career as a Data Analyst and came across the exciting roles at [Company Name].
I am reaching out to you because I admire your professional journey and expertise in the field of data analytics. Your role at [Company Name] is particularly inspiring, and I am very interested in contributing to such an innovative and dynamic team.
I am confident that my skills and enthusiasm would make me a valuable addition to this role [Job ID / Link]. If possible, I would be incredibly grateful for your referral or any advice you could offer on how to best position myself for this opportunity.
Thank you very much for considering my request. I understand how busy you must be and truly appreciate any assistance you can provide.
Best regards,
[Your Full Name]
[Your Email Address]❤6
If you're a software engineer in your 20s, beware of this habit, it can kill your growth faster than anything else.
► Fake learning.
It feels productive, but it's not.
Let me give you a great example:
You wake up fired up.
Open YouTube, start a system design video.
An hour goes by. You nod, you get it (or so you think).
You switch to a course on Spring Boot. Build a to-do app.
Then read a blog on Kafka. Scroll through a thread on Redis.
By evening, you feel like you’ve had a productive day.
But two weeks later?
You can’t recall a single implementation detail.
You haven’t written a line of code around those topics.
You just consumed, but never applied.
That’s fake learning.
It’s learning without doing.
It gives you the illusion of growth, while keeping you stuck.
📌 Here’s how to fix it:
Watch fewer tutorials. Build more things.
Learn with a goal: “I’ll use this to build X.”
After every video, write your own summary.
Recode it from scratch.
Start documenting what you really understood vs. what felt easy.
Real growth happens when you struggle.
When you break things. When you debug.
Passive learning is comfortable.
But discomfort is where the actual skills are built.
Your 20s are for laying that solid technical foundation.
Don’t waste them just “watching smart.”
Build. Ship. Reflect.
That’s how you grow.
Coding Projects:👇
https://whatsapp.com/channel/0029VazkxJ62UPB7OQhBE502
ENJOY LEARNING 👍👍
► Fake learning.
It feels productive, but it's not.
Let me give you a great example:
You wake up fired up.
Open YouTube, start a system design video.
An hour goes by. You nod, you get it (or so you think).
You switch to a course on Spring Boot. Build a to-do app.
Then read a blog on Kafka. Scroll through a thread on Redis.
By evening, you feel like you’ve had a productive day.
But two weeks later?
You can’t recall a single implementation detail.
You haven’t written a line of code around those topics.
You just consumed, but never applied.
That’s fake learning.
It’s learning without doing.
It gives you the illusion of growth, while keeping you stuck.
📌 Here’s how to fix it:
Watch fewer tutorials. Build more things.
Learn with a goal: “I’ll use this to build X.”
After every video, write your own summary.
Recode it from scratch.
Start documenting what you really understood vs. what felt easy.
Real growth happens when you struggle.
When you break things. When you debug.
Passive learning is comfortable.
But discomfort is where the actual skills are built.
Your 20s are for laying that solid technical foundation.
Don’t waste them just “watching smart.”
Build. Ship. Reflect.
That’s how you grow.
Coding Projects:👇
https://whatsapp.com/channel/0029VazkxJ62UPB7OQhBE502
ENJOY LEARNING 👍👍
❤4
📊 Preparing for a Power BI Interview? Here’s What You Need to Know!
If you're aiming for a business intelligence or analyst role, Power BI skills are a big plus.
Basics:
→ Understand what Power BI is, how to connect to data sources, and how to create simple visualizations and dashboards.
Intermediate:
→ Learn about data modeling, relationships, and using DAX (Data Analysis Expressions) for calculated columns and measures.
Advanced:
→ Dive into performance optimization, role-level security, advanced DAX functions, and integrating Power BI with tools like Excel or Azure.
🡲 Quick Tip: Build a sample dashboard and be ready to explain the decisions behind your visualizations.
React ♥️ For More
If you're aiming for a business intelligence or analyst role, Power BI skills are a big plus.
Basics:
→ Understand what Power BI is, how to connect to data sources, and how to create simple visualizations and dashboards.
Intermediate:
→ Learn about data modeling, relationships, and using DAX (Data Analysis Expressions) for calculated columns and measures.
Advanced:
→ Dive into performance optimization, role-level security, advanced DAX functions, and integrating Power BI with tools like Excel or Azure.
🡲 Quick Tip: Build a sample dashboard and be ready to explain the decisions behind your visualizations.
React ♥️ For More
❤1