GuideTechnology
16 min read
The concurrency tools you should actually use: thread pools with ExecutorService, Callable and Future, producer-consumer with BlockingQueue, ConcurrentHashMap and friends, CompletableFuture pipelines, and virtual threads from Java 21, including what they do and do not do.
GuideTechnology
12 min read
Why null causes so many bugs, what Optional is actually for, how to use map, flatMap, orElse, orElseGet and orElseThrow, and the common misuses (fields, parameters, get without a check). Optional is a tool for return values, not a universal replacement for null.
GuideTechnology
13 min read
How to process collections declaratively with Java Streams: filter, map, flatMap, sorted, reduce and collect, grouping and partitioning, why streams are lazy and single-use, what parallel streams really cost, and an honest guide to when a plain loop is the better choice.
GuideTechnology
12 min read
How Java lets you pass behaviour as a value: lambda expressions, functional interfaces and the standard Predicate, Function, Consumer and Supplier, the four kinds of method reference, composing functions, why captured variables must be effectively final, and how lambdas replace the older anonymous classes.
GuideTechnology
12 min read
How to model data precisely in modern Java: enums for fixed sets of values, records for immutable data carriers, and sealed types with pattern matching for a closed set of alternatives. Each is introduced from the bug it prevents, and compared with the older style you will still see.
GuideTechnology
13 min read
Why Java strings are immutable and what the string pool really is, when to use StringBuilder, how Unicode makes length surprising, how text blocks and formatting work, and how to handle dates and times with java.time instead of the old Date and Calendar. Includes testable time with Clock.
