From printTriangularNumber to Duff’s Device: Mastering Java Switch Statements Old and New

In this blog post, we will see how the humble Java switch statement evolved from a fall-through curiosity into a powerful expression, and how understanding its mechanics unlocks classic techniques like Duff’s Device. Java’s switch statement has evolved from a fall-through-prone construct into a modern expression syntax introduced in Java 14. The post traces this evolution using a concrete example, a method that computes triangular numbers by intentionally allowing execution to cascade through cases without break statements.