code: public static String OSX_DOCK_ICON(MinecraftDirectory minecraftDir, Set<Asset> assetIndex) {
  		Objects.requireNonNull(minecraftDir);
  		Objects.requireNonNull(assetIndex);
  		for (Asset asset : assetIndex) {
  			if ("icons/minecraft.icns".equals(asset.getVirtualPath())) {
  				return "-Xdock:icon=" + minecraftDir.getAsset(asset).getAbsolutePath();
  			}
  		}
  		return null;
  	}
docs: Caution: This option is available only on OSX.
  
  @param minecraftDir the minecraft directory
  @param assetIndex the asset index
  @return a <code>-Xdock:icon</code> option, null if the assets cannot be resolved
  @see #OSX_DOCK_ICON(MinecraftDirectory, Version)
  @see #OSX_DOCK_NAME