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

01-creational/singleton/Main.java

@@ -1,19 +1,9 @@
 package singleton;
-
 public class Main {
     public static void main(String[] args) {
-        System.out.println("=== Singleton Pattern Demo ===\n");
-
-        DatabaseConnection c1 = DatabaseConnection.getInstance();
-        DatabaseConnection c2 = DatabaseConnection.getInstance();
-        DatabaseConnection c3 = DatabaseConnection.getInstance();
-
-        System.out.println("\nAll three references same instance? " + (c1 == c2 && c2 == c3));
-
-        System.out.println(c1.executeQuery("SELECT * FROM users"));
-        System.out.println(c2.executeQuery("SELECT * FROM orders"));
-        System.out.println(c3.executeQuery("SELECT COUNT(*) FROM products"));
-
-        System.out.println("\nTotal queries: " + c1.getQueryCount());
+        AppConfig config1 = AppConfig.getInstance();
+        AppConfig config2 = AppConfig.getInstance();
+        System.out.println("Same instance? " + (config1 == config2)); // true
+        System.out.println("db.url = " + config1.getProperty("db.url"));
     }
 }