🔸 TLDR
Guarded patterns let you add a boolean condition to a pattern case using when, so you can express type + rule in one place inside a switch. Cleaner than nested if chains ✅
🔸 THE PROBLEM (JAVA 8 STYLE)
You match the type… then you nest another if for the condition. It works, but it gets noisy fast 😵💫
🔸 THE MODERN WAY (JAVA 21+)
Same logic, but expressed declaratively: “if it’s a Circle and radius > 10…” 🎯
🔸 WHY WHEN IS A BIG WIN
▪️ 🎯 PRECISE MATCHING — Type + condition in a single case label
▪️ 📐 FLAT STRUCTURE — No nested branching inside a case
▪️ 📖 READABLE INTENT — Reads almost like English (“case Circle when radius > 10”)
▪️ 🧼 EASIER TO EXTEND — Add more guarded cases without turning code into a maze
🔸 TAKEAWAYS
▪️ ✅ Use when to refine a pattern match with a boolean condition
▪️ ✅ Prefer guarded cases over “case + nested if” for readability
▪️ ✅ Great fit for classification logic (rules, routing, categorization)
▪️ ⚠️ Order matters: the first matching case wins, so put more specific guards first
#Java #Java21 #PatternMatching #SwitchExpression #CleanCode #Refactoring #SoftwareEngineering #JVM
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