A runtime format was created for Java 9, for adoption by stored classes and other resource files. This format is applicable for stored classes and resources under the following circumstances:
- When the new runtime format has greater efficiencies (time and space) than the pre-Java 9 JAR format.
A JAR file is a Java ARchive file. This is a compressed file format based on the legacy ZIP format.
- When stored classes and other resources can be individually isolated and loaded.
- When JDK and library classes and resources can be stored. This includes app modules as well.
- When they are devised in such a way as to promote future enhancements. This requires them to be extensible, documented, and flexible.