[devnexus 2022] pattern matching for Java

Speaker: Neha Sardana

Twitter: @nehasardana09

Link to table of contents

———————

Records

<missed this part; I was late>

Sealed class

  • Want to control children
  • More declarative than access modifiers
  • Can make widely accessible interface without widely extensible
  • Sets stage for pattern matching.

Pattern Matching

  • Pattern matching created in 1960s
  • Helps with clean code, avoiding repetition/bugs

Instanceof

  • matches target object to type pattern
  • sets binding variable – special case of local variables, can be assigned, can shadow field declarations
  • flow scoping – places in program where variable definitely assigned

Switch expressions

  • Limitations on switch/case are accidents of history.
  • Java 17 preview allows pattern matching in case
  • Java 19 – write ”when” instead of && in case
  • Can assign result if all cases covered. (enums and sealed classes can be listed exhaustively

Future

  • Record patterns (deconstrution patterns). ex if (r instanceof Rectangle (Point ul, Point lr))
  • Can also deconstruct arrays

My take

I thought this topic woud be fully review, but I still learned something (“when”). It was great to see Neha’s first public in person presentation! Good job!

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