Sealed-Classes on dplabs — Software Engineering & Technology Consultancy

Records and Sealed Classes: Better Domain Models in Java

Mon, 27 Jan 2025 00:00:00 +0000

Java domain modeling has historically been verbose and error-prone. Entity classes with dozens of getter/setter pairs, boolean fields that encode state (isActive, isCancelled, isPending), and null fields used to represent the absence of a value all create code that’s hard to understand and easy to misuse.

Records and sealed classes address this. They’re not cosmetic improvements — they change what kinds of mistakes the compiler can catch for you.

Records: Immutable Data Carriers

A record is a class defined by its components. The compiler generates the constructor, accessors, equals, hashCode, and toString automatically:

Pattern Matching in Modern Java: Records, Switch, and Exhaustiveness

Mon, 20 Jan 2025 00:00:00 +0000

Pattern matching in Java 21 is the culmination of several interconnected features: instanceof patterns (Java 16), sealed classes (Java 17), switch expressions (Java 14), and switch patterns (Java 21). Understanding them individually is useful. Understanding how they compose is where the real power is.

The Baseline: Pattern Matching for instanceof

Before Java 16, checking and casting looked like this:

Object shape = getShape();
if (shape instanceof Circle) {
    Circle c = (Circle) shape;  // Redundant cast
    return c.area();
} else if (shape instanceof Rectangle) {
    Rectangle r = (Rectangle) shape;
    return r.area();
}

Java 16 introduced pattern variables in instanceof:

Java 17 to 21: Modern Java Is a Different Language

Mon, 16 Dec 2024 00:00:00 +0000

Java 21 is the current long-term support release as of late 2024, and it represents something unusual: a Java that looks substantively different from Java 8. Not just faster or more convenient — different in how you model domains and reason about concurrency.

This article focuses on the features that arrived between Java 17 and Java 21 (covered separately) and the cohesive picture they form together.

Pattern Matching for Switch (Finalized Java 21)

Pattern matching for instanceof arrived in Java 16. Java 21 extended pattern matching to switch — and this is where the power becomes apparent.

Java 9 to 17: The Language Features You Should Actually Be Using

Mon, 07 Oct 2024 00:00:00 +0000

Java 8 was a turning point. Lambdas and streams changed the language substantially. Then came a long stretch where each release felt like maintenance work — modules in 9 were important but painful, and the subsequent releases improved the language incrementally without a clear headline.

That changed with Java 14–17. The features that landed in this window — records, sealed classes, pattern matching for instanceof, text blocks, switch expressions — are not conveniences. They change how you model domains and reason about code.