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Sync Adapter to Java 25: add StripePaymentClassAdapter, README mapping

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Ankur
2026-06-24 14:19:36 +05:30
parent 4b6a02f396
commit 8471913dbd
8 changed files with 60 additions and 56 deletions
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11
02-structural/adapter/Main.java
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@@ -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.");

8
02-structural/adapter/OrderService.java
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@@ -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);

2
02-structural/adapter/PaymentGateway.java
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@@ -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);

17
02-structural/adapter/README.md
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@@ -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) |
| `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 |
| 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.
## See Also

12
02-structural/adapter/StripeClient.java
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@@ -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;

24
02-structural/adapter/StripePaymentAdapter.java
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@@ -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
* via composition (not inheritance), so it can adapt any StripeClient
* including subclasses.
*
* The key responsibility: translate YOUR interface's methods into
* calls that Stripe understands — data conversion included.
* Object Adapter variant: holds a StripeClient instance via composition.
* This means it can wrap any StripeClient including subclasses.
*/
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";

23
02-structural/adapter/StripePaymentClassAdapter.java Normal file
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@@ -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";
}
}

19
README.md
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@@ -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