Guided: Java SE Pattern Matching for Enhanced Control Flow

Table of Contents

1. Challenge

   Step 1: Getting Started

   Welcome to Java SE Pattern Matching for Enhanced Control Flow. This lab modernizes a shape processing application using modern Java features: records, sealed interfaces, and pattern matching. The focus is on control-flow and branching logic—how you simplify complex decisions (geometry shapes, input validation paths, and legacy if/else chains) with concise pattern matching.

   The starter code contains traditional Java classes with verbose boilerplate. By the end, the code will be concise, type-safe, and expressive. You’ll practice the same techniques you can use in other scenarios, like validating user input safely. > This lab experience was developed by the Pluralsight team using Forge, an internally developed AI tool utilizing Gemini technology. All sections were verified by human experts for accuracy prior to publication. For issue reporting, please contact us.

2. Challenge

   Step 2: Pattern Matching with instanceof

   Modern instanceof lets you bind a variable directly in the check, removing the cast that usually follows. You'll start by cleaning up the old if/else ladder in calculateArea with pattern variables.

3. Challenge

   Step 3: Converting Classes to Records

   Java Records provide a compact syntax for immutable data classes. Each record automatically supplies a constructor, accessors, and equals/hashCode/toString, replacing a lot of boilerplate.

4. Challenge

   Step 4: Creating a Sealed Shape Hierarchy

   Sealed interfaces restrict which classes can implement them. By sealing Shape, you tell the compiler exactly which shapes exist, enabling exhaustive pattern matching in switch expressions.

5. Challenge

   Step 5: Pattern Matching with Switch

   Pattern matching for switch lets you switch directly on object types. Combined with a sealed interface, the compiler can verify you handled every shape. You'll refactor both methods in ShapeProcessor to use concise, null-safe switch expressions.

6. Challenge

   Step 6: See It in Action

   The refactoring is complete. The shape processor now uses:

   • Records for concise, immutable data classes
   • Sealed interfaces for a closed type hierarchy
   • Pattern matching for elegant, type-safe processing

   Run the demo to see the modernized code in action. Congratulations — you've finished the lab! By completing these steps you modernized a shape processor using three powerful Java features: records, sealed interfaces, and pattern matching. These changes eliminated boilerplate code, enabled compile-time type safety, and replaced verbose if-else chains with concise switch expressions.