sun.misc.resources claims to contain a ResourceBundle for sun.misc, which has localized versions of messages for "bad" jar files, such as:

  "optpkg.versionerror", "ERROR: Invalid version format used in {0} JAR file. Check the documentation for the supported version format."
  "optpkg.attributeerror", "ERROR: The required {0} JAR manifest attribute is not set in {1} JAR file."
  "optpkg.attributeserror", "ERROR: Some required JAR manifest attributes are not set in {0} JAR file."

These error message appear to not be used, either by the JDK itself, or elsewhere. I assume that there was a consumer of these at one point, but has long since been refactored away.