Sync Adapter to Java 25: add StripePaymentClassAdapter, README mapping

02-structural/adapter/Main.java

@@ -1,14 +1,5 @@
 package adapter;
 
-/**
- * Adapter Design Pattern — Runnable Demo
- *
- * Demonstrates wrapping an incompatible StripeClient behind
- * the PaymentGateway interface your application expects.
- *
- * Run: javac adapter/*.java && java adapter.Main
- * Article: https://ankurm.com/adapter-design-pattern-java/
- */
 public class Main {
 
     public static void main(String[] args) {
@@ -28,8 +19,6 @@ public class Main {
 
         // --- JDK Example: InputStreamReader as Adapter ---
         System.out.println("\n-- JDK Adapter: InputStreamReader --");
-        // InputStreamReader adapts InputStream (byte-based) to Reader (char-based)
-        // The client (BufferedReader) only knows about Reader, not InputStream
         System.out.println("InputStreamReader wraps System.in (InputStream) as a Reader.");
         System.out.println("Your code reads chars; the adapter handles byte-to-char conversion.");
 

02-structural/adapter/OrderService.java

@@ -1,25 +1,17 @@
 package adapter;
-
 /**
  * The Client — uses only the PaymentGateway interface.
  * It has no idea whether it's talking to Stripe, PayPal, or Braintree.
- * This is the point: the client is completely isolated from the vendor.
  */
 public class OrderService {
-
     private final PaymentGateway gateway;
-
-    // Receives a PaymentGateway — could be Stripe, PayPal, anything
     public OrderService(PaymentGateway gateway) {
         this.gateway = gateway;
     }
-
     public void processOrder(String orderId, String customerId, double total) {
         System.out.printf("%nProcessing order %s for customer %s, total: $%.2f%n",
                 orderId, customerId, total);
-
         boolean charged = gateway.charge(customerId, total, "USD");
-
         if (charged) {
             System.out.println("Payment accepted. Order confirmed.");
             String status = gateway.getStatus("ch_" + orderId);

02-structural/adapter/PaymentGateway.java

@@ -1,9 +1,7 @@
 package adapter;
-
 /**
  * The Target interface — what YOUR application's code expects.
  * Every payment gateway in your system must implement this.
- * Written to handle modern async-style payment flows.
  */
 public interface PaymentGateway {
     boolean charge(String customerId, double amount, String currency);

02-structural/adapter/README.md

@@ -15,17 +15,20 @@ javac adapter/*.java
 java adapter.Main
 ```
 
-Requires Java 11+.
+Requires Java 25.
 
 ## Files
 
-| File | Role |
+| Post Section | File(s) |
 |---|---|
-| `PaymentGateway.java` | Target interface (what your app expects) |
+| Step 1 — Define the Target Interface | `PaymentGateway.java` |
-| `StripeClient.java` | Adaptee (third-party SDK you can't modify) |
+| Step 2 — The Adaptee (What You're Wrapping) | `StripeClient.java` |
-| `StripePaymentAdapter.java` | Adapter (bridges the two) |
+| Step 3 — The Object Adapter | `StripePaymentAdapter.java` |
-| `OrderService.java` | Client (only uses PaymentGateway) |
+| Step 4 — The Client (Knows Nothing About Stripe) | `OrderService.java` |
-| `Main.java` | Demo entry point |
+| Putting It Together: The Main Demo | `Main.java` |
+| Object Adapter vs Class Adapter | `StripePaymentClassAdapter.java` |
+
+Note: the `InputStreamReader` JDK-adapter snippet is illustrative only — it is not part of this repository's runnable example.
 
 ## See Also
 

02-structural/adapter/StripeClient.java

@@ -1,47 +1,35 @@
 package adapter;
-
 /**
  * The Adaptee — a third-party payment SDK with a completely different interface.
  * Imagine this is Stripe's actual SDK: you cannot modify this class,
  * and it doesn't implement PaymentGateway.
- *
- * In real projects, this would be a JAR you depend on.
  */
 public class StripeClient {
-
     private final String apiKey;
-
     public StripeClient(String apiKey) {
         this.apiKey = apiKey;
         System.out.println("[Stripe] Initialized with key: " + apiKey.substring(0, 8) + "...");
     }
-
     // Stripe uses cents, not decimal amounts
     public StripeChargeResult createCharge(String customerId, long amountInCents, String currency) {
         System.out.printf("[Stripe] Charging customer=%s, amount=%d cents, currency=%s%n",
                 customerId, amountInCents, currency);
-        // Simulate success
         return new StripeChargeResult("ch_" + System.currentTimeMillis(), true, null);
     }
-
     // Stripe's refund method takes a charge ID and uses different naming
     public boolean issueRefund(String chargeId, long amountInCents) {
         System.out.printf("[Stripe] Refunding charge=%s, amount=%d cents%n", chargeId, amountInCents);
         return true;
     }
-
     // Stripe uses 'retrieve' not 'getStatus', and returns an object
     public StripeChargeResult retrieveCharge(String chargeId) {
         System.out.printf("[Stripe] Retrieving charge=%s%n", chargeId);
         return new StripeChargeResult(chargeId, true, "succeeded");
     }
-
-    // Stripe-specific result object — nothing in common with your domain
     public static class StripeChargeResult {
         public final String chargeId;
         public final boolean success;
         public final String status;
-
         public StripeChargeResult(String chargeId, boolean success, String status) {
             this.chargeId = chargeId;
             this.success = success;

02-structural/adapter/StripePaymentAdapter.java

@@ -1,42 +1,34 @@
 package adapter;
-
 /**
- * The Adapter — bridges StripeClient (Adaptee) to PaymentGateway (Target).
+ * The Adapter — bridges StripeClient to PaymentGateway.
  *
- * This is the Object Adapter variant: it holds a StripeClient instance
+ * Object Adapter variant: holds a StripeClient instance via composition.
- * via composition (not inheritance), so it can adapt any StripeClient
+ * This means it can wrap any StripeClient including subclasses.
- * including subclasses.
- *
- * The key responsibility: translate YOUR interface's methods into
- * calls that Stripe understands — data conversion included.
  */
 public class StripePaymentAdapter implements PaymentGateway {
-
     private final StripeClient stripe;
-
     public StripePaymentAdapter(StripeClient stripe) {
         this.stripe = stripe;
     }
-
     @Override
     public boolean charge(String customerId, double amount, String currency) {
-        // Translation: your code uses decimal dollars; Stripe wants integer cents
+        // Translation 1: dollars → cents
         long amountInCents = Math.round(amount * 100);
+        // Translation 2: charge() → createCharge(), lowercase currency
         StripeClient.StripeChargeResult result =
                 stripe.createCharge(customerId, amountInCents, currency.toLowerCase());
+        // Translation 3: StripeChargeResult → boolean
         return result.success;
     }
-
     @Override
     public boolean refund(String transactionId, double amount) {
-        // Translation: your "transactionId" is Stripe's "chargeId"
         long amountInCents = Math.round(amount * 100);
+        // Translation: refund() → issueRefund(), your "transactionId" is Stripe's "chargeId"
         return stripe.issueRefund(transactionId, amountInCents);
     }
-
     @Override
     public String getStatus(String transactionId) {
-        // Translation: map Stripe's object to your simple status string
+        // Translation: getStatus() → retrieveCharge(), StripeChargeResult → String
         StripeClient.StripeChargeResult result = stripe.retrieveCharge(transactionId);
         if (!result.success) return "FAILED";
         return result.status != null ? result.status.toUpperCase() : "UNKNOWN";

02-structural/adapter/StripePaymentClassAdapter.java

@@ -0,0 +1,23 @@
+package adapter;
+// Class Adapter: extends Adaptee, implements Target
+// Can only be used when you CAN extend the Adaptee (it's not final)
+public class StripePaymentClassAdapter extends StripeClient implements PaymentGateway {
+    public StripePaymentClassAdapter(String apiKey) {
+        super(apiKey);
+    }
+    @Override
+    public boolean charge(String customerId, double amount, String currency) {
+        long cents = Math.round(amount * 100);
+        return createCharge(customerId, cents, currency.toLowerCase()).success;
+        // Note: calls inherited method directly — no 'stripe.' prefix needed
+    }
+    @Override
+    public boolean refund(String transactionId, double amount) {
+        return issueRefund(transactionId, Math.round(amount * 100));
+    }
+    @Override
+    public String getStatus(String transactionId) {
+        StripeChargeResult r = retrieveCharge(transactionId);
+        return r.success ? (r.status != null ? r.status.toUpperCase() : "UNKNOWN") : "FAILED";
+    }
+}

README.md

@@ -178,6 +178,25 @@ javac 01-creational/singleton/*.java -d out/singleton
 java -cp out/singleton singleton.Main
 ```
 
+### Adapter (`02-structural/adapter/`)
+
+| Post Section | File(s) |
+|---|---|
+| Step 1 — Define the Target Interface | `PaymentGateway.java` |
+| Step 2 — The Adaptee (What You're Wrapping) | `StripeClient.java` |
+| Step 3 — The Object Adapter | `StripePaymentAdapter.java` |
+| Step 4 — The Client (Knows Nothing About Stripe) | `OrderService.java` |
+| Putting It Together: The Main Demo | `Main.java` |
+| Object Adapter vs Class Adapter | `StripePaymentClassAdapter.java` |
+
+Note: the `InputStreamReader` JDK-adapter snippet is illustrative only — it is not part of this repository's runnable example.
+
+Run it:
+```bash
+javac 02-structural/adapter/*.java -d out/adapter
+java -cp out/adapter adapter.Main
+```
+
 ## Reference
 
 - *Design Patterns: Elements of Reusable Object-Oriented Software* — Gamma, Helm, Johnson, Vlissides