Structural (Manifold :: Extensions Runtime 2026.1.6 API)

```
@Retention(RUNTIME)
@Target(TYPE)
public @interface Structural
```
Declare a structural interface using this annotation.
See the Structural Interfaces documentation for more information.

- Optional Element Summary
  
  Optional Elements
  Modifier and Type Optional Element Description
  
  Class factoryClass
  Optional.

- Element Detail
  - factoryClass
```
Class factoryClass
```
    Optional.
    A factory class that produces a proxy for a structural interface. The factory class must provide a public default constructor and must implement IProxyFactory.
    Note, the factory class exists to address performance and to facilitate proxies where structural interface methods are implemented indirectly as extension methods. In the latter case a factory class is required either here in the @Structural declaration or as a service. Note if there are more than one factory classes, they should be provided as service implementations in the META-INF/services/manifold.ext.rt.api.IProxyFactory file, or listed in your module's module-info.java file if you are using JDK 9+ with named modules.
    
    Default:
    
    java.lang.Void.class