Tag: java-8

Java Streams Advanced:Collectors, Short-Circuiting, and Pitfalls That Bite in Production

Go beyond map/filter/collect: groupingBy, teeing, takeWhile/dropWhile, short-circuit order, primitive streams, parallel pitfalls, and Stream best practices for production Java.

Java

Java Streams:Filter, Map, and Collect Without the Nested Loop Soup

A beginner-to-intermediate guide to Java Streams: source → filter/map/flatMap → collect, lazy pipelines, and when a plain for loop is clearer.

Java

CompletableFuture:Compose Async Work Without Callback Hell

Compose async Java work with CompletableFuture — supplyAsync, thenApply, thenCompose, allOf — without nested callbacks, and when virtual threads are the simpler path.

Java

java.time:Dates Without Calendar and SimpleDateFormat

Replace Calendar and SimpleDateFormat with java.time — Instant, LocalDate, ZonedDateTime, formatting, and a Clock you can fake in tests.

Java

Optional:Return Absence Without Null and Without Wrapping Every Call

Use java.util.Optional to return absence without null — of/ofNullable, map/flatMap/filter, orElse vs orElseGet, and when wrapping every call is cargo-cult.

Java

Primitive Functional Interfaces:Skip the Box on the Hot Path

Use java.util.function’s primitive SAM grid to skip boxing on hot numeric paths, fill IntStream slots, and leave ToIntFunction out of ordinary application code.

Java

Bi-Arity:Two Arguments Without a Pair Type

Use BiFunction, BiPredicate, and BiConsumer for two-argument slots — apply, test, accept — and fill Map.merge, compute, and forEach without inventing a pair type.

Java

Unary and Binary Operators:Same Type In, Same Type Out

Use UnaryOperator and BinaryOperator when input and output are the same type — List.replaceAll, Stream.reduce, Collectors.reducing, and minBy / maxBy.

Java

Supplier:Produce a Value When Asked

Use Java’s Supplier<T> for lazy values — get, orElseGet, factories, supplyAsync — so you do not build work until something actually needs the result.

Java

Consumer:Accept a Value for a Side Effect

Use Java’s Consumer<T> for side effects — accept, andThen — and see where Stream.forEach, Optional.ifPresent, and peek already ask for it.

Java

Predicate:Ask a Yes/No Question You Can Combine

Use Java’s Predicate<T> to test values — test, and, or, negate, isEqual, Predicate.not (Java 11) — and see where Stream.filter, anyMatch, and removeIf already ask for it.

Java

Function:Turn T into R Without a One-Off Interface

Use Java’s Function<T,R> to map values — apply, compose, andThen, identity — and see where Stream.map, Optional.map, and Collectors already ask for it.

Java

Functional Interfaces Roadmap:The Four Shapes Behind Every Lambda

What a Java functional interface is, the four shapes in java.util.function, when to write your own SAM type, and a living map of every post in this series.