Typical java interview questions sorted by experience


Junior
* Name some of the characteristics of OO programming languages
* What are the access modifiers you know? What does each one do?
* What is the difference between overriding and overloading a method in Java?
* What’s the difference between an Interface and an abstract class?
* Can an Interface extend another Interface?
* What does the static word mean in Java?
* Can a static method be overridden in Java?
* What is Polymorphism? What about Inheritance?
* Can a constructor be inherited?
* Do objects get passed by reference or value in Java? Elaborate on that.
* What’s the difference between using == and .equals on a string?
* What is the hashCode() and equals() used for?
* What does the interface Serializable do? What about Parcelable in Android?
* Why are Array and ArrayList different? When would you use each?
* What’s the difference between an Integer and int?
* What is a ThreadPool? Is it better than using several “simple” threads?
* What the difference between local, instance and class variables?

Mid
* What is reflection?
* What is dependency injection? Can you name a few libraries? (Have you used any?)
* What are strong, soft and weak references in Java?
* What does the keyword synchronized mean?
* Can you have “memory leaks” on Java?
* Do you need to set references to null on Java/Android?
* What does it means to say that a String is immutable?
* What are transient and volatile modifiers?
* What is the finalize() method?
* How does the try{} finally{} works?
* What is the difference between instantiation and initialisation of an object?
* When is a static block run?
* Why are Generics are used in Java?
* Can you mention the design patterns you know? Which of those do you normally use?
* Can you mention some types of testing you know?

Senior
* How does Integer.parseInt() works?
* Do you know what is the “double check locking” problem?
* Do you know the difference between StringBuffer and StringBuilder?
* How is a StringBuilder implemented to avoid the immutable string allocation problem?
* What does Class.forName method do?
* What is Autoboxing and Unboxing?
* What’s the difference between an Enumeration and an Iterator?
* What is the difference between fail-fast and fail safe in Java?
* What is PermGen in Java?
* What is a Java priority queue?
* *s performance influenced by using the same number in different types: Int, Double and Float?
* What is the Java Heap?
* What is daemon thread?
* Can a dead thread be restarted?

Source: medium.

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5 beginner-to-intermediate projects you can build if you're learning Programming & AI


1. AI-Powered Chatbot (Using Python)

Build a simple chatbot that can understand and respond to user inputs. You can use rule-based logic at first, and then explore NLP with libraries like NLTK or spaCy.

Skills: Python, NLP, Regex, Basic ML

Ideas to include:

- Greeting and small talk

- FAQ-based responses

- Sentiment-based replies

You can also integrate it with Telegram or Discord bot


2. Movie Recommendation System

Create a recommendation system based on movie genre, user preferences, or ratings using collaborative filtering or content-based filtering.

Skills: Python, Pandas, Scikit-learn

Ideas to include:

- Use TMDB or MovieLens datasets

- Add filtering by genre

- Include cosine similarity logic


3. AI-Powered Resume Parser

Upload a PDF or DOCX resume and let your app extract name, skills, experience, education, and output it in a structured format.

Skills: Python, NLP, Regex, Flask

Ideas to include:

- File upload option

- Named Entity Recognition (NER) with spaCy

- Save extracted info into a CSV/Database


4. To-Do App with Smart Suggestions

A regular to-do list but with an AI assistant that suggests tasks based on previous entries (e.g., you often add "buy milk" on Mondays? It suggests it.)

Skills: JavaScript/React + AI API (like OpenAI or custom model)

Ideas to include:

- CRUD functionality

- Natural Language date/time parsing

- AI suggestion module


5. Fake News Detector

Given a news headline or article, predict if it’s fake or real. A great application of classification problems.

Skills: Python, NLP, ML (Logistic Regression or TF-IDF + Naive Bayes)


Ideas to include:

- Use datasets from Kaggle

- Preprocess with stopwords, lemmatization

- Display prediction result with probability

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Coding Projects: https://whatsapp.com/channel/0029VazkxJ62UPB7OQhBE502

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ENJOY LEARNING 👍👍

Here's the A–Z list of essential Python programming concepts

A - Arguments
B - Built-in Functions
C - Comprehensions
D - Dictionaries
E - Exceptions
F - Functions
G - Generators
H - Higher-Order Functions
I - Iterators
J - Join Method
K - Keyword Arguments
L - Lambda Functions
M - Modules
N - NoneType
O - Object-Oriented Programming
P - PEP8
Q - Queue
R - Range Function
S - Sets
T - Tuples
U - Unpacking
V - Variables
W - While Loop
X - XOR Operation
Y - Yield Keyword
Z - Zip Function

These concepts are foundational to mastering Python and writing clean, efficient, and Pythonic code.

Credits: https://whatsapp.com/channel/0029VaiM08SDuMRaGKd9Wv0L

What is Docker ?

1 • Development

Lets say You created an Application
And that's working fine in your machine

2 • Production

But in Production it doesn't work properly
Developers experince it a lot

3 • That is when the Developer's famous words are spoken

Client - Your application is not working 😡

Developer - It's working on my Machine 😒

4 • The Reason could be due to:

• Dependencies
• Libraries and versions
• Framework
• OS Level features
• Microservices

That the developers machine has but not there in the production environment

5 • DOCKER

We need a standardized way to package the application with its dependencies and deploy it on any environment.
Docker is a tool designed to make it easier to create, deploy, and run applications by using containers.

So it will always work the same regardless of its environment

6 • How Does Docker Work?

Docker packages an application and all its dependencies in a virtual container that can run on any Linux server.

7 • Each container runs as an isolated process in the user space and take up less space than regular VMs due to their layered architecture.

Want to get started with System design interview preparation, start with these 👇

1. Learn to understand requirements
2. Learn the difference between horizontal and vertical scaling.
3. Study latency and throughput trade-offs and optimization techniques.
4. Understand the CAP Theorem (Consistency, Availability, Partition Tolerance).
5. Learn HTTP/HTTPS protocols, request-response lifecycle, and headers.
6. Understand DNS and how domain resolution works.
7. Study load balancers, their types (Layer 4 and Layer 7), and algorithms.
8. Learn about CDNs, their use cases, and caching strategies.
9. Understand SQL databases (ACID properties, normalization) and NoSQL types (key–value, document, graph).
10. Study caching tools (Redis, Memcached) and strategies (write-through, write-back, eviction policies).
11. Learn about blob storage systems like S3 or Google Cloud Storage.
12. Study sharding and horizontal partitioning of databases.
13. Understand replication (leader–follower, multi-leader) and consistency models.
14. Learn failover mechanisms like active-passive and active-active setups.
15. Study message queues like RabbitMQ, Kafka, and SQS.
16. Understand consensus algorithms such as Paxos and Raft.
17. Learn event-driven architectures, Pub/Sub models, and event sourcing.
18. Study distributed transactions (two-phase commit, sagas).
19. Learn rate-limiting techniques (token bucket, leaky bucket algorithms).
20. Study API design principles for REST, GraphQL, and gRPC.
21. Understand microservices architecture, communication, and trade-offs with monoliths.
22. Learn authentication and authorization methods (OAuth, JWT, SSO).
23. Study metrics collection tools like Prometheus or Datadog.
24. Understand logging systems (e.g., ELK stack) and tracing tools (OpenTelemetry, Jaeger).
25.Learn about encryption (data at rest and in transit) and rate-limiting for security.
26. And then practise the most commonly asked questions like URL shorteners, chat systems, ride-sharing apps, search engines, video streaming, and e-commerce websites

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15 Best Project Ideas for Backend Development : 🛠️🌐

🚀 Beginner Level :

1. 📦 RESTful API for a To-Do App
2. 📝 Contact Form Backend
3. 🗂️ File Upload Service
4. 📬 Email Subscription Service
5. 🧾 Notes App Backend

🌟 Intermediate Level :
6. 🛒 E-commerce Backend with Cart & Orders
7. 🔐 Authentication System (JWT/OAuth)
8. 🧑‍🤝‍🧑 User Management API
9. 🧾 Invoice Generator API
10. 🧠 Blog CMS Backend

🌌 Advanced Level :
11. 🧠 AI Chatbot Backend Integration
12. 📈 Real-Time Stock Tracker using WebSockets
13. 🎧 Music Streaming Server
14. 💬 Real-Time Chat Server
15. ⚙️ Microservices Architecture for Large Apps

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ENJOY LEARNING 👍👍

If I wanted to get my opportunity to interview at Google or Amazon for SDE roles in the next 6-8 months…

Here’s exactly how I’d approach it (I’ve taught this to 100s of students and followed it myself to land interviews at 3+ FAANGs):

► Step 1: Learn to Code (from scratch, even if you’re from non-CS background)

I helped my sister go from zero coding knowledge (she studied Biology and Electrical Engineering) to landing a job at Microsoft.

We started with:
- A simple programming language (C++, Java, Python — pick one)
- FreeCodeCamp on YouTube for beginner-friendly lectures
- Key rule: Don’t just watch. Code along with the video line by line.

Time required: 30–40 days to get good with loops, conditions, syntax.

► Step 2: Start with DSA before jumping to development

Why?
- 90% of tech interviews in top companies focus on Data Structures & Algorithms
- You’ll need time to master it, so start early.

Start with:
- Arrays → Linked List → Stacks → Queues
- You can follow the DSA videos on my channel.
- Practice while learning is a must.

► Step 3: Follow a smart topic order

Once you’re done with basics, follow this path:

1. Searching & Sorting
2. Recursion & Backtracking
3. Greedy
4. Sliding Window & Two Pointers
5. Trees & Graphs
6. Dynamic Programming
7. Tries, Heaps, and Union Find

Make revision notes as you go — note down how you solved each question, what tricks worked, and how you optimized it.

► Step 4: Start giving contests (don’t wait till you’re “ready”)

Most students wait to “finish DSA” before attempting contests.
That’s a huge mistake.

Contests teach you:
- Time management under pressure
- Handling edge cases
- Thinking fast

Platforms: LeetCode Weekly/ Biweekly, Codeforces, AtCoder, etc.
And after every contest, do upsolving — solve the questions you couldn’t during the contest.

► Step 5: Revise smart

Create a “Revision Sheet” with 100 key problems you’ve solved and want to reattempt.

Every 2-3 weeks, pick problems randomly and solve again without seeing solutions.

This trains your recall + improves your clarity.

Coding Projects:👇
https://whatsapp.com/channel/0029VazkxJ62UPB7OQhBE502

ENJOY LEARNING 👍👍

Most people learn SQL just enough to pull some data. But if you really understand it, you can analyze massive datasets without touching Excel or Python.

Here are 8 game-changing SQL concepts that will make you a data pro:

👇

1. Stop pulling raw data. Start pulling insights.

The biggest mistake? Running a query that gives you everything and then filtering it later.

Good analysts don’t pull raw data. They shape the data before it even reaches them.

2. “SELECT ” is a rookie move.

Pulling all columns is lazy and slow.

A pro only selects what they need.
✔️ Fewer columns = Faster queries
✔️ Less noise = Clearer insights

The more precise your query, the less time you waste cleaning data.

3. GROUP BY is your best friend.

You don’t need 100,000 rows of transactions. What you need is:
✔️ Sales per region
✔️ Average order size per customer
✔️ Number of signups per month

Grouping turns chaotic data into useful summaries.

4. Joins = Connecting the dots.

Your most important data is split across multiple tables.

Want to know how much each customer spent? You need to join:
✔️ Customer info
✔️ Order history
✔️ Payments

Joins = unlocking hidden insights.

5. Window functions will blow your mind.

They let you:
✔️ Rank customers by total purchases
✔️ Calculate rolling averages
✔️ Compare each row to the overall trend

It’s like pivot tables, but way more powerful.

6. CTEs will save you from spaghetti SQL.

Instead of writing a 50-line nested query, break it into steps.

CTEs (Common Table Expressions) make your SQL:
✔️ Easier to read
✔️ Easier to debug
✔️ Reusable

Good SQL is clean SQL.

7. Indexes = Speed.

If your queries take forever, your database is probably doing unnecessary work.

Indexes help databases find data faster.

If you work with large datasets, this is a game changer.

SQL isn’t just about pulling data. It’s about analyzing, transforming, and optimizing it.

Master these 7 concepts, and you’ll never look at SQL the same way again.

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Best Programming Languages for Hacking:

1. Python
It’s no surprise that Python tops our list. Referred to as the defacto hacking programing language, Python has indeed played a significant role in the writing of hacking scripts, exploits, and malicious programs.

2. C
C is critical language in the Hacking community. Most of the popular operating systems we have today run on a foundation of C language.
C is an excellent resource in reverse engineering of software and applications. These enable hackers to understand the working of a system or an app.

3. Javascript
For quite some time, Javascript(JS) was a client-side scripting language. With the release of Node.js, Javascript now supports backend development. To hackers, this means a broader field of exploitation.

4. PHP
For a long time now, PHP has dominated the backend of most websites and web applications.
If you are into web hacking, then getting your hands on PHP would be of great advantage.

5. C++
Have you ever thought of cracking corporate(paid) software? Here is your answer. The hacker community has significantly implemented C++ programming language to remove trial periods on paid software and even the operating system.

6. SQL
SQL – Standard Query Language. It is a programming language used to organize, add, retrieve, remove, or edit data in a database. A lot of systems store their data in databases such as MySQL, MS SQL, and PostgreSQL.
Using SQL, hackers can perform an attack known as SQL injection, which will enable them to access confidential information.

7. Java
Despite what many may say, a lot of backdoor exploits in systems are written in Java. It has also been used by hackers to perform identity thefts, create botnets, and even perform malicious activities on the client system undetected.

And then nothing works

Interview Coding Patterns

We'll cover multiple patterns asked in coding interviews. These patterns help you recognize how to approach different types of coding problems smartly — instead of solving each from scratch.

We’ll divide this into multiple parts — starting from basic and gradually going toward advanced.

Here's what we’ll cover in this section:

1. Stock Buy & Sell (Single Transaction)
2. Stock Buy & Sell (Multiple Transactions)
3. Kadane’s Algorithm (Max Subarray)
4. Sliding Window (Fixed + Variable Size)
5. Two Pointer Technique
6. Prefix Sum
7. HashMap-Based Pattern
8. Binary Search Variants
9. Backtracking Basics
10. Recursion to DP Conversion
11. Sorting-Based Tricks
12. Greedy Patterns
13. Frequency Maps and Counters
14. Stacks and Queues Based Patterns
15. Substring & Subarray Techniques

Access it for free here
👇👇
https://whatsapp.com/channel/0029VaiM08SDuMRaGKd9Wv0L/1629

7 Powerful AI Project Ideas to Build Your Portfolio

✅ AI Chatbot – Create a custom chatbot using NLP libraries like spaCy, Rasa, or GPT API
✅ Fake News Detector – Classify real vs fake news using Natural Language Processing and machine learning
✅ Image Classifier – Build a CNN to identify objects (e.g., cats vs dogs, handwritten digits)
✅ Resume Screener – Automate shortlisting candidates using keyword extraction and scoring logic
✅ Text Summarizer – Generate short summaries from long documents using Transformer models
✅ AI-Powered Recommendation System – Suggest products, movies, or courses based on user preferences
✅ Voice Assistant Clone – Build a basic version of Alexa or Siri with speech recognition and response generation

These projects are not just for learning—they’ll also impress recruiters!

#ai #projects

Top 3 coding platforms every developer should know👇

1. LeetCode: The best platform for improving skills and preparing for technical interviews.
2. CodeChef: With over 2M learners, this platform offers top courses and tech questions.
3. StackOverflow: An online community where you can find solutions to any coding question.

ENJOY LEARNING 👍👍