public JavaContainerBuilder addClasses(Path classFilesDirectory) throws IOException {
    return addClasses(classFilesDirectory, path -> true);
  }
Adds the contents of a classes directory to the image.

@param classFilesDirectory the directory containing the class files
@return this
@throws IOException if adding the layer fails
jib-core/src/main/java/com/google/cloud/tools/jib/api/JavaContainerBuilder.java