Understanding the Default Manifest
When you create a JAR file, it automatically receives a default manifest file. There can be only one manifest file in an archive, and it always has the pathname
Manifest-Version: 1.0 Created-By: 1.6.0 (Sun Microsystems Inc.)
The manifest can also contain information about the other files that are packaged in the archive. Exactly what file information should be recorded in the manifest depends on how you intend to use the JAR file. The default manifest makes no assumptions about what information it should record about other files.
Digest information is not included in the default manifest.