JEP 375: Pattern Matching for instanceof (Second Preview)

For project Amber, work is being done on pattern matching for Java, among other things. For the instanceof operator, pattern matching in Java 14 will soon become a reality. In JEP 305 – Pattern Matching for instanceof (Preview), Brian Goetz explains that pattern matching should make the Java programming language more concise and secure.

A so-called pattern is basically nothing more than a combination of a predicate for a certain target structure and a series of matching variables. If hits for the variables occur during the execution of the application, they are assigned suitable contents. The “form” of objects can thus be precisely defined, after which they are then tested by statements and expressions against their own input.

If only one type of pattern was proposed in JEP 305 (Type Test Pattern), the second preview, which was proposed as JEP 375 – Pattern Matching for instanceof (Second Preview) for JDK 15, still has the Deconstruction Pattern on board. The Type Test Pattern consists of the above predicate, which specifies a type, and a single binding variable. The Deconstruction Pattern consists of a predicate specifying a record type and several binding variables for the components of the record type.

SEE ALSO: Java 14: All the new features of JDK 14 as it hits GA

The use of pattern matching in instanceof could reduce the number of type conversions required in Java applications. In future Java versions, pattern matching could be used for further language constructs such as switch expressions.

As always, further information can be found on the OpenJDK website. Additionally, if you want to see this feature in action, check out this deep dive into pattern matching.

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