code: public static String jarVersion(JarFile jar) throws IOException {
  		String version = jar.getManifest().getMainAttributes().getValue(Attributes.Name.IMPLEMENTATION_VERSION);
  		
  		if(version == null) {
  			version = String.format("%d", System.currentTimeMillis());
  		}
  		return version;
  	}
docs: Determines the version associated with this jar
  @param jar Source jar to query version information from
  @return The source jar's version
  @throws IOException if unable to successfully query source jar