Java SE 12 ( JSR 386) (original) (raw)

A module is a named set of packages designed for reuse. A specification governed by the JCP defines standard packages, and may group them into one or more standard modules.

This Specification groups the standard packages of the Java SE Platform into 21 standard modules, which we refer to as the Java SE modules. The name of a Java SE module always starts with the string"java.". The complete list of such modules is:

java.base java.compiler java.datatransfer java.desktop java.instrument java.logging java.management	java.management.rmi java.naming java.net.http java.prefs java.rmi java.scripting java.se (aggregator)	java.security.jgss java.security.sasl java.sql java.sql.rowset java.transaction.xa java.xml java.xml.crypto

Compared to Java SE 11, this Specification does not add or remove any modules.

The module graph The Java SE modules depend upon each other as stated in their specifications, which are part of the overall API Specification. The corresponding complete Java SE module graph has too many edges to be displayed easily in visual form; here is the transitive reduction of the directed acyclic graph, in which redundant edges are omitted (click to enlarge):

Here is how to read this visualization of the module graph:

• If one module depends upon another, and it grants implied readability to that module via a requires transitive directive, then there is an edge from the first module to the second.
• At the very bottom is the java.base module, which contains essential classes such as java.lang.Object andjava.lang.String. The base module depends upon no module, and every other module depends upon the base module.
• At the top is the java.se module, which gathers together all of the modules that comprise the Java SE Platform. This is an example of an aggregator module, which logically gathers the content of other modules by granting implied readability to them, but adds no content of its own. A run-time system configured to contain the java.se module will contain all of the packages of the Java SE Platform.

A module is a Java SE module — that is, considered part of the Java SE Platform Specification — if and only if it is a standard module reachable from the java.se module.

This Specification incorporates the following subsections by reference from Java SE 9 Platform Specification (JSR 379), “Modules”:

• Constraints on Java SE modules
• Constraints on all modules in an Implementation
• Relaxing strong encapsulation
• Overriding module declarations
• Upgradeable modules