What is the best way to transform an object?

Question

Java

My object is an instance of the Port class that contains the desired portNumber field inside .

public class Port implements Serializable {
@JsonProperty("portNumber")
  private String portNumber = null;
...
}

The business logic uses a method that takes from the Port instance. But it is not Port that is returned, but the Object type.

// Возвращается инстанс Port
 runtimeService.getVariable(task.getExecutionId(), "port");

But the trouble is that I need to return the port field - portNumber. and when I try to return exactly the port field inline, the code is not very beautiful

(Port) variables.get(Variable.PORT.getName())).getPortNumber()

Is there a way to make it pretty? Maybe smack?