Sync Factory Method, Abstract Factory, Builder, Prototype to Java 25; fix post/code mismatches

01-creational/factory-method/EmailNotification.java

@@ -1,11 +1,13 @@
 package factorymethod;
 
 public class EmailNotification implements Notification {
-    private final String email;
-    public EmailNotification(String email) { this.email = email; }
 
     @Override
-    public void send(String message) {
-        System.out.println("Email -> " + email + ": " + message);
+    public void send(String recipient, String message) {
+        // In production: use JavaMail or Spring Mail
+        System.out.printf("  [EMAIL] To: %s | Body: %s%n", recipient, message);
     }
+
+    @Override
+    public String getType() { return "EMAIL"; }
 }

01-creational/factory-method/EmailSender.java

@@ -0,0 +1,8 @@
+package factorymethod;
+
+public class EmailSender extends NotificationSender {
+    @Override
+    protected Notification createNotification() {
+        return new EmailNotification();
+    }
+}

01-creational/factory-method/EmailService.java

@@ -1,11 +0,0 @@
-package factorymethod;
-
-public class EmailService extends NotificationService {
-    private final String email;
-    public EmailService(String email) { this.email = email; }
-
-    @Override
-    protected Notification createNotification() {
-        return new EmailNotification(email);
-    }
-}

01-creational/factory-method/Main.java

@@ -1,17 +1,23 @@
 package factorymethod;
 
 public class Main {
+
     public static void main(String[] args) {
-        System.out.println("=== Factory Method Pattern Demo ===\n");
 
-        NotificationService[] services = {
-            new EmailService("alice@example.com"),
-            new SmsService("+1-555-0123"),
-            new PushService("device-token-abc123")
-        };
+        // The client only knows about NotificationSender (the Creator)
+        NotificationSender sender;
 
-        for (NotificationService service : services) {
-            service.notifyUser("Your order #1042 has been shipped!");
-        }
+        sender = new EmailSender();
+        sender.notify("alice@example.com", "Your order has shipped!");
+
+        sender = new SmsSender();
+        sender.notify("+1-555-0100", "OTP: 482910");
+
+        sender = new PushSender();
+        sender.notify("device-token-xyz", "New message from Bob");
+
+        // Adding Slack: just swap the creator. Client code doesn't change.
+        sender = new SlackSender();  // new class, nothing else touched
+        sender.notify("#alerts", "CPU usage above 90%");
     }
 }

01-creational/factory-method/Notification.java

@@ -1,5 +1,11 @@
 package factorymethod;
 
 public interface Notification {
-    void send(String message);
+
+    // Every notification must know how to deliver itself
+    void send(String recipient, String message);
+
+    // Used by the Creator for logging — it needs to know the type
+    // without knowing the concrete class
+    String getType();
 }

01-creational/factory-method/NotificationSender.java

@@ -0,0 +1,31 @@
+package factorymethod;
+
+public abstract class NotificationSender {
+
+    // THE factory method — this is the one thing subclasses override.
+    // It returns a Notification (the Product interface), never a concrete class.
+    protected abstract Notification createNotification();
+
+    // The shared workflow — marked final so subclasses cannot change it.
+    // It calls createNotification() to get the right notification,
+    // then runs the same steps every time regardless of which channel was created.
+    public final void notify(String recipient, String message) {
+        Notification notification = createNotification();     // delegate creation
+        System.out.println("Sending " + notification.getType() + " notification...");
+        notification.send(recipient, message);                // use the Product interface
+        System.out.println("Delivered.");
+    }
+
+    // Shared retry logic — works for all channels without change
+    public void notifyWithRetry(String recipient, String message, int maxRetries) {
+        for (int attempt = 1; attempt <= maxRetries; attempt++) {
+            try {
+                notify(recipient, message);
+                return; // success — exit
+            } catch (Exception e) {
+                System.err.printf("Attempt %d failed: %s%n", attempt, e.getMessage());
+            }
+        }
+        throw new RuntimeException("All " + maxRetries + " attempts failed");
+    }
+}

01-creational/factory-method/NotificationService.java

@@ -1,11 +1,24 @@
 package factorymethod;
 
-/** Creator - declares the factory method */
-public abstract class NotificationService {
-    protected abstract Notification createNotification();
+public class NotificationService {
 
-    public void notifyUser(String message) {
-        Notification n = createNotification();
-        n.send(message);
+    public void send(String type, String recipient, String message) {
+
+        // Creation logic mixed with business logic
+        Notification notification;
+        if ("EMAIL".equals(type)) {
+            notification = new EmailNotification();
+        } else if ("SMS".equals(type)) {
+            notification = new SmsNotification();
+        } else if ("PUSH".equals(type)) {
+            notification = new PushNotification();
+        } else {
+            throw new IllegalArgumentException("Unknown type: " + type);
+        }
+
+        // Business logic that should never change
+        System.out.println("Sending " + type + " to " + recipient);
+        notification.send(recipient, message);
+        System.out.println("Delivered.");
     }
 }

01-creational/factory-method/PushNotification.java

@@ -1,11 +1,13 @@
 package factorymethod;
 
 public class PushNotification implements Notification {
-    private final String deviceToken;
-    public PushNotification(String deviceToken) { this.deviceToken = deviceToken; }
 
     @Override
-    public void send(String message) {
-        System.out.println("Push -> " + deviceToken + ": " + message);
+    public void send(String recipient, String message) {
+        // In production: use Firebase FCM
+        System.out.printf("  [PUSH]  To: %s | Alert: %s%n", recipient, message);
     }
+
+    @Override
+    public String getType() { return "PUSH"; }
 }

01-creational/factory-method/PushSender.java

@@ -0,0 +1,8 @@
+package factorymethod;
+
+public class PushSender extends NotificationSender {
+    @Override
+    protected Notification createNotification() {
+        return new PushNotification();
+    }
+}

01-creational/factory-method/PushService.java

@@ -1,11 +0,0 @@
-package factorymethod;
-
-public class PushService extends NotificationService {
-    private final String token;
-    public PushService(String token) { this.token = token; }
-
-    @Override
-    protected Notification createNotification() {
-        return new PushNotification(token);
-    }
-}

01-creational/factory-method/SlackNotification.java

@@ -0,0 +1,11 @@
+package factorymethod;
+
+// New Concrete Product — knows how to send to Slack
+public class SlackNotification implements Notification {
+    @Override
+    public void send(String recipient, String message) {
+        System.out.printf("  [SLACK] Channel: %s | Message: %s%n", recipient, message);
+    }
+    @Override
+    public String getType() { return "SLACK"; }
+}

01-creational/factory-method/SlackSender.java

@@ -0,0 +1,9 @@
+package factorymethod;
+
+// New Concrete Creator — knows to create a SlackNotification
+public class SlackSender extends NotificationSender {
+    @Override
+    protected Notification createNotification() {
+        return new SlackNotification();
+    }
+}

01-creational/factory-method/SmsNotification.java

@@ -1,11 +1,13 @@
 package factorymethod;
 
 public class SmsNotification implements Notification {
-    private final String phone;
-    public SmsNotification(String phone) { this.phone = phone; }
 
     @Override
-    public void send(String message) {
-        System.out.println("SMS -> " + phone + ": " + message);
+    public void send(String recipient, String message) {
+        // In production: use Twilio SDK
+        System.out.printf("  [SMS]   To: %s | Text: %s%n", recipient, message);
     }
+
+    @Override
+    public String getType() { return "SMS"; }
 }

01-creational/factory-method/SmsSender.java

@@ -0,0 +1,8 @@
+package factorymethod;
+
+public class SmsSender extends NotificationSender {
+    @Override
+    protected Notification createNotification() {
+        return new SmsNotification();
+    }
+}

01-creational/factory-method/SmsService.java

@@ -1,11 +0,0 @@
-package factorymethod;
-
-public class SmsService extends NotificationService {
-    private final String phone;
-    public SmsService(String phone) { this.phone = phone; }
-
-    @Override
-    protected Notification createNotification() {
-        return new SmsNotification(phone);
-    }
-}