For decades, Java has drawn a clear distinction between primitive types and reference types, with each category following its own rules in the language. One of those rules was simple: instanceof applies to reference types, not primitives. That separation has shaped how generations of Java developers reason about type checks and conversions.
One of our speakers at OCX 26, Manoj Nalledathu Palat, who leads work on the Java compiler at IBM, explains in an interview that this design choice was intentional. “It is illegal in classic Java, and fairly so,” he says, reflecting the original meaning of instanceof as a check tied to type derivation. What is changing now is not that rule itself, but the context in which Java developers increasingly use pattern matching, and the need for a more uniform way to reason about types across the language.
So why is Java revisiting this rule now?
The answer lies in how developers increasingly use pattern matching. “If you want to apply that pattern matching uniformly to both reference type and primitive types, then you need to bring in that concept,” Manoj explains. When instanceof is reframed as a way to ask whether a value can be safely treated as a particular type, rather than whether it is derived from one, primitives begin to fit the bill in the expanded meaning of instanceof.
This shift is not about making Java more permissive. It is about making existing behaviour more explicit, especially around primitive conversions. Manoj highlights a risk many teams underestimate: there is this risk of a silent bug being introduced when implicit primitive conversions occur. Unlike reference types, where invalid casts surface as runtime exceptions, primitive overflows and narrowing conversions can fail quietly and remain undetected.
To address this, Java introduces stronger compiler guarantees. Manoj says, “the compiler is with you on this,” describing checks that act as “a primitive’s answer to a class cast exception”. Rather than relying purely on developer discipline, the language increasingly provides guardrails that make unsafe assumptions visible.
Importantly, Primitives in Patterns is a preview feature. It is not something developers should adopt in production today. Instead, it offers insight into where the Java language is heading, and why long-held mental models around primitives are being carefully and deliberately updated.
Primitives in patterns - Providing foundational changes to next-gen Java types
In his session at the Open Community Experience 2026, Manoj Nalledathu Palat will help you rethink how Java treats primitives and reference types, and where the remaining differences still matter in real code. You will leave with a clearer mental model of primitive conversions, their risks, and the language guarantees the compiler provides.
