`Optional::stream` (Java 9+) bridges optionals into the Stream API — collect all the `Some` values from a list of optionals, drop the empties, in one pipeline.
`EXTRACT(field FROM timestamp)` pulls year, month, hour, day-of-week, week, epoch — whatever you need to group, filter, or render. Standard SQL across every database.
Compile-time code generation for JSON serialization. Annotate `@Serializable` on a data class; `Json.encodeToString` and `Json.decodeFromString` are typed.
Comments and reviews can also have Schema.org markup. The `Review` type appears under products in Google search results with star ratings; `Comment` is for general user feedback.
`<T>` declares a type parameter. Use it on classes (`Box<T>`) and functions (`fun <T> identity(x: T) = x`). Type bounds (`T : Comparable<T>`) constrain what T can be.
Modern dataclass essentials: immutable instances (frozen=True), tighter memory + faster attribute access (slots=True), and default_factory for mutable defaults so every instance gets its own list.
Use PHP's built-in FILTER_VALIDATE_EMAIL with the FILTER_FLAG_EMAIL_UNICODE flag for IDN domains, plus a length sanity check. Trust this over hand-rolled regex.
Parse the standard HTTP Link header (RFC 5988) into a relation → URL map. Lets you follow rel="next" pagination in APIs like GitHub without manually building URLs.
`strconv.Atoi` / `Itoa` for the common int<->string case; `ParseFloat`, `ParseBool`, `Quote` for everything else. Always handle the error — strings can be anything.
Map each element to a Stream, then concatenate all of them into one. Used everywhere from "all words from a list of sentences" to "all permissions from a list of roles".
docker-compose entrypoints often need to wait for a sibling service (DB, cache) to be healthy before starting work. Poll the health-check status until healthy or timeout.
A single-arg method/extension can be called without dot or parens when marked `infix`. Lets you write DSL-style code like `5 shouldBe 5` or `key to value`.
Java 21's virtual threads are millions-of-them cheap — JVM multiplexes them onto a small carrier pool. Replaces async/reactive code for most I/O-bound workloads: just write blocking code that doesn't actually block a kernel thread.