Multi-release JAR files will have a new attribute, Multi-Release: true. This attribute will be located in the JAR MANIFEST.MF main section.
The directory structure will differ between standard JAR files and multi-release JAR files. Here is a look at a typical JAR file structure:
Javadoc directory tree
The following illustration shows the new multi-release JAR file structure with Java version-specific class files for both Java 8 and Java 9:
JAR file structure