# Pattern Matching

> Pattern matching is a set of language features that allow you to test the structure or type of a value and extract components from it in a single, concise expression. Java has added pattern matching incrementally since Java 14, progressively ...

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Pattern matching is a set of language features that allow you to test the structure or type of a value and extract components from it in a single, concise expression. Java has added pattern matching incrementally since Java 14, progressively replacing verbose, error-prone type-checking idioms.

The simplest form is pattern matching for `instanceof` (finalised in Java 16): instead of writing `if (obj instanceof String) { String s = (String) obj; }`, you write `if (obj instanceof String s)`. The cast and variable declaration are fused into the pattern.

The more powerful form is pattern matching in `switch` expressions and statements (finalised in Java 21). Combined with sealed classes, a `switch` can exhaustively match every subtype of a sealed hierarchy, and the compiler verifies at compile time that all cases are covered. This makes data-oriented programming in Java significantly more concise and safe.

## See Also

* [Switch Expressions](/pedia/switch-expressions/)
* [Records](/pedia/records/)
* [Sealed Classes](/pedia/sealed-classes/)
* [Project Amber](/pedia/project-amber/)