The array is the most fundamental data structure in computer science, forming the backbone of more complex collections like ArrayList. A deep understanding o...

Rays is a powerful, enterprise-grade Dependency Injection (DI) and Inversion of Control (IoC) framework for Go, built by BeamFoundry. - BeamFoundry/rays

Arrays, ArrayList, LinkedList, HashMap, TreeMap, stacks and queues in Java: what each one is good at, a Big-O cheat sheet, and the mistakes that cost performance.

Merge two sorted lists in Java in O(n + m): the two-pointer solution for ArrayList, a generic version, and the LeetCode 21 linked-list solution with tests.

# Python for Java Developers: A Complete Bridge Guide You're a 10-year Java veteran. Now you need to learn Python. Here's how to use your Java knowledge. ## Mental Model Shifts ### 1. Dynamic vs Static Typing Java: List<String> names = new ArrayList<>(); names.add("Alice"); Python: names = [] names.append("Alice") Python figures out types at runtime. No generics. Use type hints for clarity: names: list[str] = [] ### 2. Indentation is Syntax Java uses braces. Python uses indentation. // Java if (x > 5) { doSomething(); } # Python if x > 5: do_something() Indentation _is_ the code structure. No exceptions. ### 3. Everything is an Object Like Java, but more extreme. Functions, classes, modules—all objects. def greet(name): return f"Hello, {name}" # Functions are objects func = greet result = func("Alice") # "Hello, Alice" ### 4. No `new` Keyword // Java Person p = new Person("Alice"); # Python p = Person("Alice") Constructor calls look like function calls. ## Java ↔ Python Equivalents Java | Python ---|--- `String` | `str` `int`, `long`, `double` | `int`, `float` `List<T>` | `list` `Map<K,V>` | `dict` `Set<T>` | `set` `try/catch/finally` | `try/except/finally` `@Override` | No decorator needed `interface` | Protocol or ABC `synchronized` | `threading.Lock` ## Building a REST API (Familiar Territory) ### Java (Spring Boot): @RestController public class UserController { @GetMapping("/users/{id}") public User getUser(@PathVariable Long id) { return userService.find(id); } } ### Python (FastAPI): from fastapi import FastAPI app = FastAPI() @app.get("/users/{user_id}") def get_user(user_id: int): return user_service.find(user_id) Concepts are identical. Syntax is simpler in Python. ## Async/Await (Java 21+ Virtual Threads vs Python asyncio) ### Java: CompletableFuture.supplyAsync(() -> fetchUser(id)) .thenApply(this::processUser) .thenAccept(System.out::println); ### Python: async def process(): user = await fetch_user(id) result = process_user(user) print(result) Python's async is more readable. Java's model is more powerful (virtual threads). ## Testing Patterns ### Java (JUnit 5): @Test void testUserCreation() { User user = new User("Alice"); assertEquals("Alice", user.getName()); } ### Python (pytest): def test_user_creation(): user = User("Alice") assert user.name == "Alice" Same concepts, less boilerplate. ## Dependency Management ### Java: Maven/Gradle ### Python: pip/poetry # Python pip install requests flask poetry add django ### Virtual Environments (Python) Essential to avoid conflicts. Like Maven repositories per project. python -m venv venv source venv/bin/activate # On Windows: venv\Scripts\activate pip install requests ## Common Pitfalls for Java Developers ### 1. Mutability of Default Arguments # ❌ WRONG def append_item(item, items=[]): items.append(item) return items append_item(1) # [1] append_item(2) # [1, 2] - NOT [2]! # ✅ CORRECT def append_item(item, items=None): if items is None: items = [] items.append(item) return items ### 2. String Immutability Python strings are immutable (like Java), but loops can be slow: # ❌ SLOW result = "" for char in "hello": result += char # Creates new string each time # ✅ FAST result = "".join(char for char in "hello") ### 3. The Global Interpreter Lock (GIL) Python's threading isn't true parallelism (GIL locks). Use processes or async: from multiprocessing import Pool with Pool(4) as p: results = p.map(expensive_function, items) ## Where Python Shines (for Java Developers) * **Rapid prototyping** : Less ceremony, faster to MVP * **Data science** : NumPy, Pandas, scikit-learn ecosystem * **ML/AI** : TensorFlow, PyTorch, LangChain * **Scripting** : Great for automation tasks * **Readable code** : Forces you to write clear code ## Where Java Still Wins * **Performance-critical systems** : JIT compilation beats Python * **Large teams** : Static typing catches bugs earlier * **Ecosystem maturity** : Spring, Hibernate, etc. are rock-solid * **Concurrency** : Virtual threads, structured concurrency * **Type safety** : Refactoring is safer ## Your Migration Path 1. **Week 1** : Learn syntax, data structures, control flow 2. **Week 2** : Build a REST API with FastAPI 3. **Week 3** : Work with databases (SQLAlchemy ORM) 4. **Week 4** : Pick a specialization (ML, data, web) You already know OOP, design patterns, testing, CI/CD. That transfers 100%. Just learn Python idioms. ## Recommended Learning Resources * Automate the Boring Stuff with Python (free online) * FastAPI Tutorial (official docs—excellent) * Real Python (deep dives on specific topics) * Build a project (Flask/FastAPI app) You've conquered Java. Python will feel easy. The hardest part? Unlearning the need for type annotations and semicolons.

Hello guys, cracking the coding interview is not easy anymore, even for experienced developers because software engineering interview has completely changed now. Gone are the days when we can just remember ArrayList vs LinkedList and ArrayList vs Vector and get a job, now there are multiple rounds, with take home test, CoderPad or HackerRank test, live coding and System Design. If you still want to be employable then you need to adapt and learn things which matters like Coding Patterns and System Design. When I first started preparing seriously for coding interviews at top tech companies like Meta, Google, and Amazon, I did what most people do — I jumped straight into LeetCode, picked random problems, and hoped for the best. But the results were mixed. I would often solve a problem only to forget the approach a week later. That’s when I discovered AlgoMonster — and my approach to Data Structures and Algorithms changed for good. AlgoMonster isn’t just another collection of problems. It’s a pattern-based system for solving coding questions. It teaches you to first identify the pattern before jumping into code — whether it’s sliding window, binary search, two pointers, or BFS/DFS. Each pattern has well-organized theory, real examples from tech interviews, and problems arranged by difficulty level. They even have pattern-specific ladders for Meta, Google, and Amazon — something I haven’t seen anywhere else, not even on platforms like Exponent, ByteByteGo, Educative, or DesignGuru. AlgoMonster Practice Tool — Solve Coding Problem by Identify Patterns One of my favorite parts is their Monster 50 and Blind 75 lists. Instead of just practicing blindly, AlgoMonster guides you to approach each problem with a strategy-first mindset: * Identify the pattern * Sketch the solution * Implement the code * Analyze the time and space complexity This step-by-step process ingrains the right habits. Over time, I stopped panicking when I saw a tough question. I started recognizing familiar patterns, and that boosted both my accuracy and confidence in mock interviews. It was like seeing the matrix. Their coding platform is also very top notch similar to what you will find in Exponent, Educative, and HackerRank. Here is how AlgoMonster’s Coding Interview Practice tool look like You can try their practice tool here, its complete free, just click on the Practice Tab. How much AlgoMonster cost? Talking about cost and fees, another huge advantage of AlgoMonster is? Price. AlgoMonster is one of the most affordable platforms available today. Their lifetime plan costs only a few hundred dollars, and compared to the thousands charged by InterviewKickstart or other bootcamps, it’s an absolute steal. You get: * Lifetime access to curated content * Regularly updated problems * Guided solutions with analysis * Strategy built for FAANG and Tier-1 companies To top it off, the Reddit community has tons of positive reviews and real success stories. People talk about how they went from struggling with brute-force thinking to identifying optimal solutions thanks to the structure AlgoMonster provides. If you’re serious about cracking coding interviews and want to save both time and money, I genuinely believe AlgoMonster is the best way to go. Is it really worth to get a AlgoMonster PRO lifetime membership for $459 (U.P. $918) now? For more practice, you can even combine AlgoMonster with LeetCode to cement your understanding. Use AlgoMonster to learn the patterns, and LeetCode to reinforce them through volume. That combo worked wonders for me. You can also combine AlgoMonster with Exponent which provides mock interviews. By creating a free Exponent account you can do interview with peers. They give 5 interviews to everybody and credit also replenish over time when you receive positive feedback. You can check Exponent’s mock interview tool here. Final Thoughts That’s all about why Algomonster is the best platform for learning and practicing Data Structures and Algorithms for coding interviews. Unlike traditional platforms where you’re overwhelmed with problem sets and little guidance, AlgoMonster acts like a mentor — helping you build strong fundamentals through patterns. If I had to choose between AlgoMonster and Exponent, ByteByteGo, Educative, or DesignGuru. — especially for coding problems — I’d go with AlgoMonster without hesitation. Another great thing about them is that they are offering 50% discount now, and the value it provides, AlgoMonster is definitely worth it. Here is the link to join Algomoster now for a 50% discount Other System Design and Coding Interview and Resources you may like * 16 Best Resources for System Design Interview Prep * Is DesignGuru’s System Design Course worth it * ByteByteGo vs NeetCode vs Educative? which one is better? * Is ByteByteGo a good place for Coding interviews? * 3 Free Books and Courses for System Design Interviews * Is System Design Interview RoadMap by DesignGuru worth it? * Is Exponent’s System Design Course worth it? * 10 Best Places to Learn System Design in 2027 * How to Prepare for System Design Interview in 2027 * Is ByteByteGo worth the hype? * My Favorite Software Design Courses for 2027 * ByteByteGo 50% OFF? Should you Join? * 10 Reasons to Learn System Design in 2027 * 6 Best System Design and API Design Interactive Courses * Top 5 System Design YouTube Channels for Engineers * 3 Places to Practice System Design Mock interviews * 20 System Design Interview Questions for Practice * Is Designing Data-intensive application book worth reading? All the best for your Coding Interviews, if you have any doubts or questions, feel free to ask in the comments. P. S. — If you just want to do one thing at this moment, go join Algomonster and start learning DSA Concepts and practice coding interviews you will thank me later. It’s one of the most comprehensive resource for coding interview now. --- Java, Unix, Tibco RV and FIX Protocol Tutorial

Looking for the best functional programming course for Java? These 6 courses cover Java Lambdas, Functional Interfaces, Streams, Method References, Optional, Collectors, and modern functional-style programming. Hello friends, Functional programming has become an important part of modern Java development. If you’ve been writing Java for a while, you’ve probably seen code like this:List names = new ArrayList(); for (User user : users) { if (user.isActive()) { names.add(user.getName()); } } Modern Java lets you express the same idea much more declaratively:List names = users.stream() .filter(User::isActive) .map(User::getName) .toList(); That’s the appeal of functional programming in Java. Instead of describing every step the computer needs to perform, you can describe what you want to do with the data. Java introduced lambda expressions and the Stream API in Java 8, and subsequent releases have continued to make Java more expressive. Today, functional-style programming is part of everyday Java development rather than an optional advanced technique. And if you’re preparing for Java interviews, functional programming is particularly useful because Lambdas, Streams, Functional Interfaces, Optional, and Collectors regularly appear in coding exercises and interview discussions. So, if you’re looking for the best functional programming courses for Java developers in 2026, you’ve come to the right place. I looked at popular Java functional-programming courses across Udemy, Coursera, and Educative, paying particular attention to: * Course freshness * Java version coverage * Lambdas * Functional interfaces * Stream API * Method references * Collectors * Optional * Immutability * Higher-order functions * Parallel streams * Hands-on exercises * Interview preparation * Real-world Java development Here are the six courses I’d put on your shortlist.Disclosure: This article contains affiliate links. If you purchase a course through one of these links, I may earn a commission at no additional cost to you. 6 Best Functional Programming Courses for Java Developers in 2026 Here are my favorite online courses to learn Functional programming in Java and master lambda, stream and other functional programming concepts in depth. 1. Learn Java Functional Programming with Lambdas & Streams Platform: Udemy Instructor: in28Minutes Official Length: 6+ hours Rating: 4.6/5 Students: 56,000+ If you want one straightforward course to get started with functional programming in Java, this is still one of the first courses I’d consider. The course currently has more than 56,000 students and 11,000 ratings, and it covers the fundamentals developers typically need when moving from imperative Java programming to functional-style Java. The course focuses on: * Lambda expressions, Functional interfaces, Method references * Stream API, Intermediate stream operations, and Terminal operations * Predicate, Consumer, Supplier, Function, BinaryOperator * Higher-order functions * Behavior parameterization * Parallel streams * Working with Lists and Maps * Files, Threads, and Coding exercises One feature I particularly like is the use of Java puzzles and exercises rather than simply explaining Stream API syntax. You get to practice transformations such as:numbers.stream() .filter(n -> n % 2 == 0) .map(n -> n * n) .forEach(System.out::println); rather than simply memorizing what filter() and map() mean. What you’ll learn The course starts with functional programming fundamentals and gradually moves toward:Lambda Expressions ↓ Functional Interfaces ↓ Method References ↓ Streams ↓ Stream Operations ↓ Higher-Order Functions ↓ Parallel Streams ↓ Real Java Applications The curriculum also includes a large Q&A-style review section covering functional interfaces, parallel streams, higher-order functions, and related concepts. Who should take it? This course is particularly suitable for: * Java developers new to functional programming * Developers who understand Java OOP but struggle with Streams * Developers preparing for Java interviews * Spring Boot developers who want to write more modern Java * Developers moving from Java 7-style code to modern Java My take If you’re searching for a Java functional programming course for beginners, this is an easy course to start with. Here is the link to join this course — Learn Java Functional Programming with Lambdas & Streams Learn Java Functional Programming with Lambdas & Streams 2. Java Functional Programming: Lambdas, Streams & Collections Platform: Udemy Instructor: Ramesh Fadatare Length: 19+ hours Rating: 4.7/5 Last updated: September 2026 If course freshness matters to you, this is one of the most interesting options on the list. The course was updated in September 2026 and currently contains more than 19 hours of material across 160+ lectures. It also takes a slightly broader approach than many short functional-programming courses. Instead of immediately jumping into:stream() the course spends time on the Java Collections Framework, which makes sense because Streams are frequently used to process collections. It also includes coding exercises and real-world use cases. Why the Collections section matters A common mistake is learning Streams without understanding collections. For example:List users = ... Then immediately:users.stream() But you should understand: * Why you’re using a List * When a Set makes more sense * How Map differs from List * What HashMap does * What ordering means * How collections are transformed That’s why I like the broader approach of this course. Who should take it? Choose this course if you want: * A newer course * Lots of coding examples * Collections + functional programming * Comprehensive Stream API coverage * Interview-oriented practice * A longer course than the typical 3–6 hour Lambda course My take For someone searching specifically for a modern Java functional programming course in 2026, this is one of the newer options worth checking. Here is the link to check this course — Java Functional Programming: Lambdas, Streams & Collections Java Functional Programming: Lambdas, Streams & Collections 3. Functional Java: Master Java Lambdas and Streams Platform: Udemy Instructor: Java Brains Length: 5+ hours Rating: 4.8/5 If you’re interested in understanding why functional programming works, rather than simply memorizing Stream operations, this course is worth considering. The course covers concepts such as: * Functional programming principles * Pure functions and Impure functions * First-class functions * Higher-order functions * Functional interfaces * Lambda expressions * Method references * Closures * Immutability * Function composition * Stream API * Lazy evaluation * Parallel processing * Functional-style concurrency The course currently contains around 5 hours of material and 47 lectures. One particularly useful topic is function composition. For example:Function doubleIt = x -> x * 2;Function addTen = x -> x + 10; Function result = doubleIt.andThen(addTen); The point isn’t simply learning andThen(). It’s understanding that functions can be treated as reusable pieces that can be composed together. Why this matters There’s a difference between knowing:list.stream() .filter(...) .map(...) .collect(...); and understanding the underlying concepts:Functions ↓ Composition ↓ Immutability ↓ Declarative programming ↓ Stream pipelines The latter gives you a much stronger foundation. Who should take it? This course is particularly interesting for: * Experienced Java developers * Developers transitioning from OOP to functional programming * Developers interested in clean code * Developers interested in immutability * Developers who want to understand function composition My take If you’ve already used Streams but feel like you’re using functional programming without really understanding it, this is the type of course I’d explore. Here is the link to join this course — Functional Java: Master Java Lambdas and Streams Functional Java: Master Java Lambdas and Streams 4. Functional Programming in Java: Java Lambdas and Streams Platform: Udemy Instructor: Dr. Seán Kennedy Last updated: January 2026 Sometimes you don’t need a 30-hour Java course. You already know: * Java syntax * OOP * Collections * Generics You simply want to become comfortable with:Lambdas Functional Interfaces Method References Streams That’s where a focused course can be useful. This course was updated in January 2026 and focuses specifically on Java Lambdas and Streams. For example, you’ll learn how the relationship between an interface and lambda expression works:Predicate even = number -> number % 2 == 0; And then use it:numbers.stream() .filter(even) .toList(); Why I like focused courses A focused course has one major advantage: You don’t have to spend 20 hours relearning Java. If you’re already comfortable with Java, you can go directly into the concepts you actually need. Here is the link to join this course — Functional Programming in Java: Java Lambdas and Streams Functional Programming in Java : Java Lambdas and Streams 5. Functional Programming with Java and Threads (Coursera) Platform: Coursera If you’re an experienced Java developer, functional programming becomes even more interesting when combined with concurrency. This Coursera course covers both object-oriented and functional programming, then connects those concepts with modern Java concurrency. The curriculum covers: * Lambda expressions * Method references * Functional interfaces * Functional design * Java concurrency * Threads * Asynchronous computation * Virtual threads * Future * FutureTask * Scalable programming The course description specifically includes modern Java concurrency concepts such as virtual threads alongside functional programming. That’s valuable because functional programming and concurrency have an interesting relationship. Pure functions are easier to reason about because they minimize hidden state and side effects. For example:int square(int x) { return x * x; } Compare that with code that modifies shared mutable state. When multiple threads execute code concurrently, avoiding unnecessary shared mutable state can make programs easier to reason about. If you’ve already mastered basic Lambdas and Streams, I’d rather see you connect functional programming with concurrency, immutability, and scalability than spend another five hours learning basic filter() examples. Here is the link to join this course — Functional Programming with Java and Threads 6. Java 8 for Experienced Developers: Lambdas, Stream API & Beyond (Educative.io) If you’re already an experienced Java developer and want to go deeper into modern Java rather than taking a beginner functional-programming course, Pluralsight’s Java SE Deep Dive path is worth considering. The current path contains 15 courses and 11 labs, with a dedicated section covering functional programming with Lambdas, Generics, and Streams. It includes a Java SE Deep Dive: Lambda Expressions course updated in March 2026 and a Streams course covering streams from pipelines through newer functionality such as Gatherers. This is particularly interesting for developers who don’t want to stop at:stream() .filter() .map() .collect(); The modern Java ecosystem continues to evolve. Why this is different The other courses on this list are mostly standalone functional-programming courses. You can use the learning path to continue into other modern Java topics rather than treating functional programming as an isolated skill. Here is the link to join this course — Java 8 for Experienced Developers: Lambdas, Stream API & Beyond And, if you find the Educative platform and their interactive courses useful then you can also get an Educative Subscription that provides access to not just this course but their 210+ courses in just $14.9 per month. It’s very cost-effective and great for preparing for coding interviews Educative Unlimited: Excel with AI-Powered Learning Final Thoughts Functional programming is no longer an exotic concept in Java. If you’re working with modern Java, you will almost certainly encounter:Lambdas Streams Functional Interfaces Method References Optional Collectors The trick is not to turn every Java program into a giant chain of .map().filter().flatMap() calls. The goal is to understand when functional-style code makes your program clearer. If you’re a beginner, start with a practical course such as Learn Java Functional Programming with Lambdas & Streams. If you want a newer and broader course, Java Functional Programming: Lambdas, Streams & Collections is worth checking out. If you’re an experienced developer, consider going deeper into immutability, function composition, concurrency, and modern Java Streams rather than simply learning Lambda syntax. And most importantly:Don’t just watch a functional programming course. Rewrite your existing Java code. Take an old for loop. Turn it into a Stream. Then ask yourself: Is the new version actually easier to understand? That’s when functional programming starts becoming a useful engineering skill rather than just another item on your Java resume. One final tip: don’t buy six functional programming courses. Buy one. Finish it. Then write some code. The fastest way to learn Java functional programming is still to open your IDE and start replacing those 50-line loops with small, readable transformations — and then decide whether the result is actually better. All the best !!. --- I Tried 20+ Java Functional Programming Courses — Here Are My Top 6 Recommendations for 2027 was originally published in Javarevisited on Medium, where people are continuing the conversation by highlighting and responding to this story.

## Summary `RedisArrayAggregator` recently added `maxElements` and `maxNestedArrayDepth` limits to fix public Redis resource-exhaustion advisories. The limits are independent, but the allocator remains eager: every positive nested RESP array header creates `new ArrayList (length)` before any child element exists. With the default constructor, an attacker can send nested array headers with …

Sorting/Searching using ArrayList DUE: Tuesday October 18 by 10PM SHARP! Problem Description: In this assignment, you will modify a solution to Assignment 1. You may use your solution, or my posted one. You will make the Bank data structure more efficient in two ways. a) Change the bankData declaration in Bank class to be an object of ArrayList.. b) Add to the menu an option to display the database – which will display each element in the array.

Problem Description: In this assignment, you will complete an objectoriented version of the software managing Bank customers’ Bank Accounts. Note you may NOT use the ArrayList class in Java for this assignment. We will use this assignment as the base for many following assignments. You must use the classes as named in this assignment, but you can use different methods and data member names as long as your solution follows all Object Oriented Principles.

Concepts tested by this program: ArrayList Tooltips Mnemonic Read Files Javadoc JUnit Tests Exceptions Create an application that will check for valid passwords. The following rules must be followed to create a valid password. 1.At least 6 characters long 2.More than 10 characters is a strong password, between 6 and 10 characters is a weak (but acceptable) password. 3.At least 1 numeric character&hellip;

Added enumeration handling when the internal ArrayList has already been loaded but an enumeration follows. This fixes the issue with 9.x Linq statements against the collection caused by the access ...

My last article about generic data structures in C was written to set the stage for today’s topic: A data structure with constant time indexing, stable pointers, and works well with arena allocators. ...