Question

Instead of using if/else I’d like to use a map to get a concrete implementation.

I’d like to use generics to declare a specific entity handler witch handles a specific entity but I have the problem that the handler just accepts extensions of my entity interface. The code looks like this:

private Map<Class<IEntity>, IEntityHandler> handlers;

public void callingMethod(IModel model) {
  for (IEntity entity : model.getObjects()) {
    // handle accepts just IDevice and not IEntity !
    handlers.get(entity).handle(entity);
  }
}

public interface IEntityHandler<T extends IEntity> {
  handle(T entity);
}

public class DeviceHandler implements IEntityHandler<IDevice> {
  @Override
  public void handle(IDevice deviceEntity) {
    // do something
  }
}

How can I get my handle method that it takes IEntity’s? IDevice extends from IEntity.

Answer 1

Declare you map as:

Map<Class<T extends IEntity>, IEntityHandler> handlers.