Strategy Pattern: Choosing Algorithms at Runtime

interview, best-practices

java java21 scala scala3 kotlin design-patterns strategy-pattern

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Coming Soon — We're Still Hammering This One Out This post is on the roadmap and is being actively crafted. Think of it as a movie trailer: the good stuff is coming, you just caught us before the popcorn was ready. Check back soon — or bookmark the series guide to track all posts as they land.
⏳  Post in progress

What You'll Learn When This Post Is Ready

• How to avoid massive if-else chains by replacing conditional logic with Strategy objects
• How to define interchangeable algorithms behind a common interface and swap them at runtime
• How lambda expressions and first-class functions in Java, Scala, and Kotlin simplify strategy implementations
• How dependency injection often doubles as a strategy selector — and why that's elegant
• A real-world payment processing example: tax calculation strategies for different countries
• Side-by-side comparison across Java 21, Scala 3, and Kotlin with full test coverage

Interview Questions You Can Expect

• “How would you implement different payment processing strategies without a giant switch statement?”
• “What is the relationship between the Strategy pattern and lambda expressions?”
• “When do you use the Strategy pattern instead of plain if-else statements?”
• “Can you compose strategies together? Show an example.”
• “How does dependency injection relate to the Strategy pattern?”