The modular JDK

The core aim of JEP-200 was to modularize the JDK using the Java Platform Module System (JPMS). Prior to Java 9, our familiarity with the JDK includes awareness of its major components:

• The JRE
• The interpreter (Java)
• The compiler (Javac)
• The archiver (JAR)
• The document generator (Javadoc)

The task of modularizing the JDK was to break it into components that could be combined at compile time or runtime. The modular structure is based on the following modular profiles established as compact profiles in Java 8. Each of the three profiles is detailed in the following tables:

• Compact profile 1:

    
java.io           java.lang.annotation           java.lang.invoke

      
java.lang.ref           java.lang.reflect           java.math

      
java.net           java.nio           java.nio.channels

      
java.nio.channels.spi           java.nio.charset           java.nio.charset.spi

      
java.nio.file           java.nio.file.attribute           java.nio.file.spi

      
java.security           java.security.cert           java.security.interfaces

      
java.security.spec           java.text           java.text.spi

      
java.time           java.time.chrono           java.time.format

      
java.time.temporal           java.time.zone           java.util

      
java.util.concurrent           java.util.concurrent.atomic           java.util.concurrent.locks

      
java.util.function           java.util.jar           java.util.logging

      
java.util.regex           java.tuil.spi           java.util.stream

      
java.util.zip           javax.crypto           javax.crypto.interfaces

      
javax.crypto.spec           javax.net           javax.net.ssl

      
javax.script           javax.security.auth           javax.security.auth.callback

      
javax.security.auth.login           javax.security.auth.spi           javax.security.auth.spi

      
javax.security.auth.x500           javax.security.cert           
  

• Compact profile 2:

    
java.rmi           java.rmi.activation           java.rmi.drc

      
java.rmi.registry           java.rmi.server           java.sql

      
javax.rmi.ssl           javax.sql           javax.transaction

      
javax.transaction.xa           javax.xml           javax.xml.database

      
javax.xml.namespace           javax.xml.parsers           javax.xml.stream

      
javax.xml.stream.events           javax.xml.stream.util           javax.xml.transform

      
javax.xml.transform.dom           javax.xml.transform.sax           javax.xml.transform.stax

      
java.xml.transform.stream           javax.xml.validation           javax.xml.xpath

      
org.w3c.dom           org.w3c.dom.bootstrap           org.w3c.dom.events

      
org.w3c.dom.ls           org.xml.sax           org.xml.sax.ext

      
org.xml.sax.helpers                      
  

• Compact profile 3:

    
java.lang.instrument           java.lang.management           java.security.acl

      
java.util.prefs           javax.annotation.processing           javax.lang.model

      
javax.lang.model.element           javax.lang.model.type           javax.lang.model.util

      
javax.management           javax.management.loading           javax.management.modelmbean

      
javax.management.monitor           javax.management.openmbean           javax.management.relation

      
javax.management.remote           javax.management.remote.rmi           javax.management.timer

      
javax.naming           javax.naming.directory           javax.naming.event

      
javax.naing.ldap           javax.naming.spi           javax.security.auth.kerberos

      
javax.security.sasl           javax.sql.rowset           javax.sql.rowset.serial

      
javax.sql.rowset.spi           javax.tools           javax.xml.crypto

      
javax.xml.crypto.dom           javax.xml.crypto.dsig           javax.xml.crypto.dsig.dom

      
javax.xml.crypto.dsig.keyinfo           javax.xml.crypto.dsig.spec           org.ieft.jgss
  

The three compact module profiles represent the basis for the standardized modular system in the current Java platform. The effectiveness of this standardization relies on the following six principles:

• All JCP-governed modules must start with the string java. So, if a module on spatial utilities was being developed, it would have a name such as java.spatial.util.

• Non-JCP modules are considered part of the JDK and their names must start with the string jdk.
• Ensure method invocation chaining works properly. This is best illustrated with the following flowchart:

As you can see in the preceding flowchart, it only applies to modules that export a package.

• The fourth principle deals with both standard and nonstandard API packages being used in a standard module. The following flowchart illustrates the implementation of this principle's covenants:

• The fifth design principle is that standard modules can be dependent upon more than one nonstandard module. While this dependency is permitted, implied readability access to nonstandard modules is not. 
• The final design principle ensures nonstandard modules do not export standard API packages.