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

02-structural/proxy/RealDatabaseConnection.java

@@ -0,0 +1,33 @@
+package proxy;
+
+/**
+ * Real Subject — the actual, expensive database connection.
+ * Opening it takes time. We want to delay this until truly needed.
+ */
+public class RealDatabaseConnection implements DatabaseConnection {
+
+    private final String url;
+
+    public RealDatabaseConnection(String url) {
+        this.url = url;
+    }
+
+    @Override
+    public void connect() {
+        System.out.println("[Real DB] Connecting to " + url + " (expensive operation)...");
+        // Simulate connection setup time
+        try { Thread.sleep(100); } catch (InterruptedException e) { Thread.currentThread().interrupt(); }
+        System.out.println("[Real DB] Connected.");
+    }
+
+    @Override
+    public String executeQuery(String sql) {
+        System.out.println("[Real DB] Executing: " + sql);
+        return "ResultSet{rows=42}";  // simulated result
+    }
+
+    @Override
+    public void disconnect() {
+        System.out.println("[Real DB] Disconnecting from " + url);
+    }
+}