Decorator vs Imperative

decorator-vs-imperative.java

Image image = new RotatedImage( // just a regular declaration
  CLOCKWISE, 
  90,
  new GrayScaledImage(
    new CachedImage(
      "//cdn.google.com/logos/apple.png",
      new RemoteImage("//cdn.google.com/logos/apple.png")
    )
  )
);

return image.bytes(); // all magic happens heere

// vs imperative approach

ImageService {
  RemoteImageService remoteImages;
  ImageCache cache;

  byte[] getImage(String uri) {
    Image image = cache.get(uri)
    if(image != null) {
      return image;
    }
    image = remoteImages.getImage(uri);
    if(image != null) {
      return image;
    }
    ImageUtils.grayscale(image);
    ImageUtils.rotate(image, CLOCKWISE, 90);
    return image;
  }
}

1. Image is an interface
2. We DECLARE what image is, instead of MANIPULATING it
3. Imagine how do you order stuff in a store? Do you say "whole grain sandwich with hummus & long-ripening cheese, please" or rather: "take a sandwich, put butter on bottom, put long-ripening cheese, put hummus, close sandwich, wrap with napkin and give it to me"?
4. each different Image implementation is easy to reuse, easy to test, easy to modify (cause is small & cohesive)
5. each Image impl is lazy
6. Image is closed for modifications & open for extensions easily in contrary to ImageService approach

• it is very easy for everyone to add more modificators to image (e.g. SaturatedImage, etc.), in imperative approach it would result in ImageService becoming a god class (or ImageUtils)