Add all 23 GoF design pattern implementations (2026-06-13)

02-structural/adapter/README.md

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+# Adapter Design Pattern — Java Example
+
+**Pattern:** Structural → Adapter
+**Article:** https://ankurm.com/adapter-design-pattern-java/
+
+## What this example shows
+
+Wraps a third-party `StripeClient` (with its own API) behind a `PaymentGateway` interface that your application code expects. The `OrderService` client never touches `StripeClient` directly — it only sees `PaymentGateway`. Swapping payment providers requires changing one line.
+
+## How to run
+
+```bash
+# From this folder:
+javac adapter/*.java
+java adapter.Main
+```
+
+Requires Java 11+.
+
+## Files
+
+| File | Role |
+|---|---|
+| `PaymentGateway.java` | Target interface (what your app expects) |
+| `StripeClient.java` | Adaptee (third-party SDK you can't modify) |
+| `StripePaymentAdapter.java` | Adapter (bridges the two) |
+| `OrderService.java` | Client (only uses PaymentGateway) |
+| `Main.java` | Demo entry point |
+
+## See Also
+
+- Full article: https://ankurm.com/adapter-design-pattern-java/
+- All design patterns: https://ankurm.com/design-patterns-java/