Let's look at the layout of the content in mr.jar:
jar -tvf mr.jar
The contents of the JAR is as shown in the following:
The preceding layout we have META-INF/versions/9 which contains the Java 9 specific code. Another important thing to note is the contents of the META-INF/MANIFEST.MF file. Let's extract the JAR and view its contents:
jar -xvf mr.jar$ cat META-INF/MANIFEST.MFManifest-Version: 1.0Created-By: 9 (Oracle Corporation)Main-Class: com.packt.FactoryDemoMulti-Release: true
The new manifest attribute Multi-Release is used to indicate if the JAR is a multirelease JAR or not.