Run the jar tool without arguments to see its usage. You pass it the -M option to create a JAR without a manifest. You won't be able to run the JAR file with java -jar, but you will still be able ...

This post introduces you to multi-release JAR files. Discovering multi-release JAR files Many third-party Java frameworks and libraries support several versions of the Java platform.

Newer versions of Java now require all JAR files to be signed with a valid code-signing key, and starting with Java 7 Update 51, unsigned or self-signed applications are blocked from running.