The Core Libraries Group

ThisGroup is comprised ofdevelopers who participate in the design, implementation, andmaintanence of the Java core libraries.

Introduction

The core libraries consist of classes which are used by manyportions of the JDK. The actual set of files has evolved over time,but mostly they include functionality which is close to the VM andis not explicitly included in other areas, such asSecurity orNetworking. Also included are commonlyused tools which are either built on top of the core libraries(such asjar) or are used by developersworking with them (such asrmic).

Feature Areas

The following table lists the feature areas of the corelibraries with their corresponding repository locations and linksto other developer documentation. (For documentation targeted forJDK users rather than contributors, see the sectionEnd-User Documentation.)

Currently there are some libraries which appear in the namepackages as core libraries but are maintained by other groups.These exceptions are mentioned within the corresponding tableentries.

Unless otherwise specified, all locations are in thejdk repository.

Feature Area	Repository Locations	More Information
java.lang Provides classes that are fundamental to the design of the Javaprogramming language such as`String`,`Math`,`Enum`, and the wrapper classes for primitive types (e.g.`Boolean`,`Float`,`Character`).	`src/share/classes/java/lang` `src/share/native/java/lang` `src/solaris/classes/java/lang` `src/solaris/native/java/lang` `src/windows/classes/java/lang` `src/windows/native/java/lang` `test/java/lang`	Bugs ClassLoader API Modification for Deadlock Fix v.04 (Updated: March 312009)
Threading Includes basic runtime support for threads.	`src/share/classes/java/lang/Thread.java` `src/share/native/java/lang/Thread.c` `test/java/lang/Thread`	Bugs
Process Includes basic runtime support for creating processes andcontrolling process I/O.	`src/share/classes/java/lang/Process.java` `src/share/classes/java/lang/ProcessBuilder.java` `src/share/classes/java/lang/Runtime.java` `src/share/native/java/lang/Runtime.c` `src/solaris/classes/java/lang/Process` `src/windows/classes/java/lang/Process` `src/solaris/native/java/lang/Process` `src/windows/native/java/lang/Process` `test/java/lang/ProcessBuidler` `test/java/lang/Runtime`	Bugs
java.lang.annotationjavax.annotation Provides library support for the Java programming languageannotation facility. (These are closely related to the Compiler APIandjavax.lang.model, which are all owned by theCompiler Group.	`jdk repository:` `src/share/classes/java/lang/annotation` `src/share/classes/sun/reflect/annotation` `langtools repository:` `src/share/classes/javax/annotationsrc/share/classes/javax/lang/model`	JSR 269:`java.lang.annotation` package java.lang.annotationBugs javax.annotationBugs
java.lang.instrument Provides services that allow Java programming language agents toinstrument programs running on the JVM. These APIs are owned by theServiceabilityGroup	`src/share/classes/java/lang/instrument` `src/share/classes/sun/instrument` `src/share/instrument` `src/solaris/instrument` `src/windows/instrument` `test/java/lang/instrument`	See theServiceability Group
java.lang.management Provides the management interface for monitoring and managementof the JVM as well as the operating system on which the JVM isrunning. These APIs are owned by theServiceability Group	`src/share/classes/java/lang/management` `test/java/lang/management`	See theServiceability Group
java.lang.ref Provides reference-object classes, which support a limiteddegree of interaction with the garbage collector.	`src/share/classes/java/lang/ref` `src/share/native/java/lang/ref` `test/java/lang/ref`	Bugs
java.lang.reflect Provides classes and interfaces for obtaining reflectiveinformation about classes and objects.	`src/share/classes/java/lang/reflect` `src/share/classes/sun/reflect` `src/share/native/java/lang/reflect` `src/share/native/sun/reflect` `test/java/lang/reflect` `test/java/lang/Class`	Bugs
java.io Provides for system input and output and the file system.	`src/share/classes/java/io` `src/share/native/java/io` `src/solaris/classes/java/io` `src/solaris/native/java/io` `src/windows/classes/java/io` `src/windows/native/java/io` `test/java/io`	Bugs
Serialization Supports encoding of objects to and from byte streams.	`src/share/classes/java/io/Externalizable.java` `src/share/classes/java/io/ObjectInputStream.java` `src/share/classes/java/io/ObjectOutputStream.java` `src/share/classes/java/io/NotSerializableException.java` `src/share/classes/java/io/Serializable.java` `src/share/classes/java/io/SerializablePermission.java` `src/share/native/java/io/ObjectInputStream.c` `src/share/native/java/io/ObjectOutputStream.c` `test/java/io/Externalizable` `test/java/io/ObjectInputStream` `test/java/io/Serializable`	Java Object Serialization Specification Bugs
`serialver` Tool retrieves the`serialVersionID` for a class.	`src/share/classes/sun/tools/serialver` `test/java/io/Serializable/serialver`	Unix reference page Windows reference page
java.nio Provides buffers to contain data of primitive type.	`src/share/classes/java/nio` `src/share/classes/sun/nio/ByteBuffered.java` `src/share/native/java/nio` `src/solaris/native/java/nio` `src/windows/native/java/nio` `test/java/nio/Buffer` `test/java/nio/ByteOrder` `test/java/nio/MappedByteBuffer` `make/gensrc/GensrcBuffer.gmk`	JSR 51:`java.nio` packages for channels and charsets buffer, channels, and file systemBugs
java.nio.channels java.nio.channels.spi Defines channels, an abstraction for devices capable ofperforming I/O operations; defines selectors for multiplexed,non-blocking I/O.	`src/share/classes/java/nio/channels` `src/share/classes/sun/nio/ch` `src/share/native/sun/nio/ch` `src/share/sample/nio` `src/solaris/classes/sun/nio/ch` `src/solaris/native/sun/nio/ch` `src/windows/classes/sun/nio/ch` `src/windows/native/sun/nio/ch` `test/java/nio/channels` `test/sun/nio/ch` `src/share/sample/nio`
java.nio.charset java.nio.charset.spi Defines charsets, decoders, and encoders, for translatingbetween bytes and Unicode characters	`src/share/classes/java/nio/charset` `src/share/classes/sun/nio/cs` `src/solaris/classes/sun/nio/cs` `make/gensrc/GensrcCharsetCoder.gmk`	Supported Encodings Bugs
`native2ascii` Tool converts files to and from native encodings.	`src/share/classes/sun/tools/native2ascii` `test/sun/tools/native2ascii`	Unix reference page Windows reference page Bugs
java.nio.file java.nio.file.attribute java.nio.file.spi Defines interfaces and classes to access files, file attributes,and file systems.	`src/share/classes/java/nio/file` `src/share/classes/com/sun/nio/file`	JSR 203:`java.nio` packages for file system Bugs
java.util Provides the collections framework, formatted printing andscanning, array manipulation utilities, event model, date and timefacilities, internationalization, and miscellaneous utilityclasses.	`src/share/classes/java/util` `test/java/util`	Bugs
Collections Includes all classes which implement the`Collection`interface such as data structures implementing lists, queues, maps,and sets.	`src/share/classes/java/util/ArrayDeque.java` `src/share/classes/java/util/ArrayList.java` `src/share/classes/java/util/Collection.java` `src/share/classes/java/util/Collections.java` `src/share/classes/java/util/Map.java` `src/share/classes/java/util/Set.java` `src/share/classes/java/util/Linked.java` `src/share/classes/java/util/Stack.java` `src/share/classes/java/util/Vector.java` `test/java/util/ArrayDeque.java` `test/java/util/ArrayList.java` `test/java/util/Collection.java` `test/java/util/Collections.java` `test/java/util/Map.java` `test/java/util/Set.java` `test/java/util/Linked.java` `test/java/util/Stack.java` `test/java/util/Vector.java`	Bugs
Internationalization Classes Includes support for internationalization and locale-specificoutput of dates, times, and currencies. These APIs are owned by theInternationalizationGroup	`src/share/classes/java/util/Calendar.java` `src/share/classes/java/util/Currency.java` `src/share/classes/java/util/Date.java` `src/share/classes/java/util/Locale.java` `src/share/classes/java/util/ResourceBundle.java` `src/share/classes/java/util/TimeZone.java` `src/share/classes/sun/util/*.java (exceptPreHashedMap.java)` `src/share/classes/sun/util/resources`	See theInternationalizationGroup Bugs
java.util.concurrent java.util.concurrent.atomic java.util.concurrent.locks Provides utility classes used in concurrent programming,including support for atomic updates of single variables and alocking framework which supplements language-levelsynchronization.	`src/share/classes/java/util/concurrent` `src/share/native/java/util/concurrent` `test/java/util/concurrent`	JSR 166:`java.util.concurrent*` packages Maintainer'swebsite Bugs
java.util.jar Provides classes for reading and writing the JAR (Java ARchive)file format.	`src/share/classes/com/sun/java/util/jar` `src/share/classes/java/util/jar` `src/share/native/com/sun/java/util/jar` `test/java/util/jar` Not strictly part of JAR, but useful: `src/share/classes/sun/net/www/protocol/jar` `src/solaris/classes/sun/net/www/protocol/jar` `src/windows/classes/sun/net/www/protocol/jar` `test/sun/net/www/protocol/jar`	JAR File Specification `java.util.{jar,zip}`Bugs `jarsigner` is owned by theSecurity Group
`jar` Tool creates and accesses the contents of a`.jar` file.	`src/share/classes/sun/tools/jar` `test/tools/jar`	Unix reference page Windows reference page Bugs
`extcheck` Tool detects conflicts between a target`.jar` file and thecurrently installed extension`.jar` files.	`src/share/classes/com/sun/tools/extcheck`	Unix reference page Windows reference page Bugs in the extension mechanism, including`extcheck`
java.util.logging Provides support to maintain and service software at customersites.	`src/share/classes/java/util/logging` `src/share/classes/sun/util/logging` `test/java/util/logging`	Bugs
java.util.regex Provides classes for matching character sequences againstpatterns specified by regular expressions.	`src/share/classes/java/util/regex`	Bugs
java.util.prefs Provides classes to store and retrieve user and systempreference and configuration data.	`src/share/classes/java/util/prefs` `src/solaris/classes/java/util/prefs` `src/windows/classes/java/util/prefs`	Bugs
java.util.spi Service provider classes for the java.util package. These APIsare owned by theInternationalization Group	`src/share/classes/java/util/spi`	See theInternationalizationGroup
java.util.stream Classes to support function-style operations on streams ofelements, such as map-reduce transformations on collections.	`src/share/classes/java/util/stream` `test/java/util/stream`	Bugs
java.util.zip Provides classes for reading and writing the standard ZIP andGZIP file formats.	`src/share/classes/java/util/zip` `src/share/native/java/util/zip` `test/java/util/zip`	Bugs
java.math Provides classes for performing arbitrary-precision integerarithmetic (`BigInteger`) and arbitrary-precision decimalarithmetic (`BigDecimal`).	`src/share/classes/java/math` `src/share/classes/java/lang/Math.java` `src/share/classes/java/lang/StrictMath.java` `src/share/classes/sun/misc/FloatConsts.java` `src/share/classes/sun/misc/FloatingDecimal.java`	JSR 13:`BigDecimal` enhancements Bugs
java.rmi java.rmi.activation java.rmi.dgc java.rmi.registry java.rmi.server Provides support for remote communication between programswritten in Java.	`src/share/classes/java/rmi` `src/share/classes/sun/rmi` `test/java/rmi` `test/sun/rmi`	Remote Invocation Home Page Java RMI Specification Bugs
`rmic` Toolgenerates stub, skeleton, and tie classes for remote objects usingeither the JRMP or IIOP protocols, and generates OMG IDL.	`src/share/classes/java/rmi/rmic` `test/sun/rmi/rmic`	Unix reference page Windows reference page
`rmid` Tool starts the activation system daemon that allows objects to beregistered and activated in a VM.	`src/share/classes/com/sun/rmi/rmid`	Unix reference page Windows reference page
`rmiregistry` Tool starts a remote object registry on the specified port on thecurrent host.	`src/share/classes/sun/rmi/registry`	Unix reference page Windows reference page
java.sql javax.sql Provides the API for accessing and processing data stored indata source.	`src/share/classes/java/sql` `src/share/classes/javax/sql` `src/share/classes/com/sun/rowset`
javax.naming javax.naming.directory javax.naming.event javax.naming.ldap javax.naming.spi Provides access to Naming and Directory Service such as DNS andLDAP.	`src/share/classes/javax/naming` `src/share/classes/com/sun/naming` `test/javax/naming` `src/share/classes/com/sun/jndi` `test/com/sun/jndi`	JavaNaming and Directory Interface Home Page Bugs
javax.script Provides interfaces and classes that define Java ScriptingEngines and a framework for their use in Java applications. JDK 8 includes source code for the Nashorn script engine whichis based on JSR 292's`invokedynamic`.	`jdk repository:` `src/share/classes/javax/script` `src/share/classes/com/sun/script` `src/share/demo/scripting/jconsole.plugin` `src/share/sample/scripting` `test/javax/script` `nashorn repository:` `src/*`	JSR 223:scripting support JSR 292:`invokedynamic` javax.scriptBugs NashornBugs
`jrunscript` Tool provides a command line script shell both both interactive andbatch modes of script execution. This tool is experimental and unsupported.	`src/share/classes/com/sun/tools/script` `test/sun/tools/jrunscript`	Unix reference Page Windows reference Page
javax.xml javax.xml.datatypejavax.xml.namespacejavax.xml.parsersjavax.xml.streamjavax.xml.stream.eventsjavax.xml.stream.utiljavax.xml.transformjavax.xml.transform.comjavax.xml.transform.saxjavax.xml.transform.staxjavax.xml.transform.streamjavax.xml.validationjavax.xml.xpathorg.w3c.domorg.w3c.dom.bootstraporg.w3c.dom.lsorg.w3c.dom.viewsorg/xml/sax org/xml/sax.ext org/xml/sax.helpers The Java API for XML Processing (JAXP) enables applications toparse, transform, validate, and query XML documents using an APIthat is independent of a particular XML processorimplementation.	`jaxp repository:` `src/*`	JSR 206:JAXP 1.3 Java API for XML Processing(JAXP) at Project GlassFish

Building

Developers arestrongly encouraged to perform fullbuilds prior to check-in of any changes. (Afull build isa build performed when there is no pre-existingbuilddirectory; the respository should contain only the desired changesand no auto-generated data. Simply performingmake at thetop of the build tree isnot a full build.) Depending onthe area, incremental builds are not a reliable indicator ofwhether or not changes will compile successfully in a full build.In particular, some files are used early in the bootstrap phase tobuild components likejava.lang.Object, the launcher, andjavac that are used to build the rest of the JDK. Theseare later re-built once sufficient infrastructure has beengenerated by the bootstrap build. Incremental builds will onlycatch errors that occur in the compile after bootstrap.

Even when it appears that onlyjava code is beingmodified, it is prudent to build on multiple platform families. Arecommended minimum is one Windows and one Unix target, butdepending on the code being modified, it may be necessary toinclude a wider spectrum or a specific set of platforms. This isnecessary because there is no guarantee that thejava codewhich depends on a change in core is identical on all platforms.For instance,rt.jar is not portable—the classeswithin it vary from platform to platform.

Testing

Tests or modifications of existing tests are required and mustaccompany all changes (both new functionality and any bug fixes).There are some exceptions. For example, it is not always possibleto provide test for fixes for performance problems or otherconditions that are difficult to simulate or require unusualenvironmental conditions (such as exceptionally low memory, systemreboot, third-party software, etc.).

In addition to running the new tests, tests in the modified areaand any dependent areas should be run. Dependent areas may not beimmediately obvious. As with builds, it is necessary to run testson multiple platforms.

Not all areas have tests in the repository. There are twopossible reasons for this. It may be that there are no tests ortests may exist, but have not been audited for open-sourcing. Inthe latter case, the goal is to add them soon. Please ask aboutappropriate testing when considering a modification.

End-UserDocumentation

The following links reference the canonical end-userdocumentation for the JDK. The features areas listed above willhave documentation in the corresponding sections of thesereferences.

JDK 8Documentation
The features areas listed above will have documentation in thecorresponding sections of this reference which includes releasenotes describing the history of feature updates.
The JavaTutorials
The majority of core functionality is described in the section"Trails Covering the Basics". Additional topics may be found in the"Specialized Trails and Lessons" section.

Community

Mailing lists
- core-libs-dev
- jdbc-spec-discuss

Core libraries bloggers
- Alan Bateman
  Specification Lead forJSR 203: "More New I/OAPIs for the Java Platform ("NIO.2")"
- Joe Darcy
  Specification Lead forJSR 269:"PluggableAnnotation Processing API" and Floating-point Czar

Members

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