How a developer using the interface can build their code without access to a class that implements the interface. The developer using the interface can create a temporary mock object, sometimes referred to as dummy code, which simulates the real object that implements the interface with a simple implementation. The mock object does not need to be very complex, with one line per abstract method, for example, as it only serves as a placeholder for the real implementation. This allows the developer using the interface to compile, run, and test their code.