transient sclass ThumbnailCache {
  gettable WidthAndHeightImpl thumbnailSize = new(100);
  
  // max bytes in memory
  settable long maxBytes;
  
  // estimated bytes in memory
  gettable long totalBytes;
  
  new TheMap map;
  
  transient Lock lock = lock();
  
  class TheMap extends LinkedHashMap<File, BufferedImage> {
    @Override
    protected bool removeEldestEntry(Map.Entry<File, BufferedImage> eldest) {
      if (totalBytes > maxBytes) {
        totalBytes -= guessImageBytes(eldest.getValue());
        true;
      }
      false;
    }
  }
  
  int guessImageBytes(BufferedImage image) {
    // 24 is a random guess for the overhead of an image
    ret 24+guessImageSizeInMemory(image);
  }
  
  BufferedImage makeThumbnail(File file) {
    ret loadImage2(file);
  }
  
  selfType thumbnailSize(int wAndH) {
    ret thumbnailSize(new WidthAndHeightImpl(wAndH));
  }
  
  selfType thumbnailSize(WidthAndHeightImpl size) {
    lock lock;
    if (eq(thumbnailSize, size)) this;
    thumbnailSize = size;
    map.clear();
    this;
  }
  
  synchronized BufferedImage get(File imageFile) {
    lock lock;
    if (map.containsKey(imageFile))
      ret map.get(imageFile);
    var img = makeThumbnail(imageFile);
    totalBytes += guessImageBytes(img);
    map.put(imageFile, img);
    ret img;
  }
}