I am doing this within a Factory class' `getInstance()` method, reading the fully-qualified name of a class from a properties file and creating an instance of that class.

```java
    static IAuthenticationManager getInstance() throws Exception{
        if (instance == null){
            instance = new AuthenticationManagerFactory();
        }

        String type = props.getProperty(AUTH_MANAGER_TYPE);
        Class<?> c = Class.forName(type);
        return (IAuthenticationManager) c.getDeclaredMethod("getInstance").invoke(null);
    }
```