and I know a jar file uses the zip format. But how does one create a jar file without a manifest file. (I don't mean creating a zip file and renaming it jar. That'd be cheating). As would creating ...

In review, the steps to digitally sign JAR files with jarsigner, assuming you have Java installed, are: Create a JAR file with Java’s JAR utility Create public and private keys with Java’s keytool ...

You must create a JAR folder in your project, then specify the JAR file you want to include in your application. The JAR is automatically included with the app when you run it on your device.