Calling External APIs with RestClient (Spring Boot 3.2+)
Guide to using RestClient for HTTP API calls: GET/POST, error handling, timeouts, interceptors, HTTP interfaces, and testing with MockRestServiceServer.
ConcurrentHashMap vs HashMap and Collections.synchronizedMap
Compare HashMap, Collections.synchronizedMap, and ConcurrentHashMap on thread-safety, locking mechanisms, iterators, null handling, and performance, with examples and tests.
Configuring tsconfig for a New TypeScript Project
Guide to setting up tsconfig.json for new TypeScript projects, covering strict mode, NodeNext module, separating build/test configurations, and common pitfalls.
Enum and pattern matching in Rust
How to define enums with data, use match, if let, and let else to handle each case safely, plus common mistakes when working with enums in Rust.
equals() and hashCode(): Contract and Common Pitfalls
Understand the contract between equals() and hashCode() in Java, how to implement them correctly, and common mistakes that cause HashSet and HashMap to misbehave.
Generics in Go: type parameters through examples
Learn how to use type parameters, constraints, the ~ notation, and generic types in Go through Order, Customer, Stack, and Cache examples.
Iterators and Closures in Rust
Learn about closures, the three traits Fn/FnMut/FnOnce, how to use iterator adapters like map, filter, and collect, and how to write custom iterators in Rust.
Kotlin Collection: map, filter and groupBy with practical examples
How to use map, filter, groupBy and their variants like mapNotNull, partition, groupingBy to process collections in Kotlin clearly and correctly.
Kotlin Flow: Asynchronous data streams
Learn Kotlin Flow from basics: flow builder, operators, flowOn, error handling, StateFlow/SharedFlow and how to test with runTest.
List, dict, set comprehension in Python: concise yet readable
How to use list, dict, set comprehension and generator expressions in Python for concise and readable code, including common pitfalls and when to return to for loops.
Spring Boot Actuator: Health Checks and Metrics
Configure Spring Boot Actuator for health checks, liveness/readiness probes, and metrics with Micrometer, including export to Prometheus.
Type guard and assertion function in TypeScript
How to use type guard (x is T) and assertion function (asserts x is T) to safely narrow types, validate unknown data, and avoid common pitfalls.
Writing tests with pytest and fixtures in Python
A guide to writing tests with pytest, using fixtures to prepare data, clean up resources, share via conftest.py, and parameterize tests.
CompletableFuture: Asynchronous Execution and Combining Results
Use CompletableFuture in Java 21 to call several services in parallel, chain and combine results, handle errors and timeouts, and write tests for asynchronous code.
Configuration with @ConfigurationProperties Instead of @Value
Group configuration into a typed record with @ConfigurationProperties. This guide covers binding complex types, startup validation, IDE metadata, and testing.
Context Managers and the with Statement in Python
Understand how the with statement works, write your own context managers using classes or contextlib, handle exceptions properly, and avoid common pitfalls.
Discriminated Unions in TypeScript for State and API Response
Use discriminated unions to model state and API responses, letting the compiler block invalid states and remind you to handle all cases.
Error Handling in Go: errors.Is, errors.As, and Error Wrapping
How to wrap errors with %w, check errors across the wrap chain with errors.Is, extract custom errors with errors.As, combine errors with errors.Join, and common pitfalls.
Interfaces in Go: Small, Implicit, and Done Right
Go interfaces are implicitly satisfied. This guide shows how to keep interfaces small, declare them at the point of use, test with fakes, and avoid common pitfalls like nil interfaces.
Sealed classes and pattern matching for switch in Java 21
Use sealed classes, pattern matching for switch, and record patterns in Java 21 to replace chains of if-instanceof with shorter, compiler-verified code.