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Proposed new [[Java]] page. See this "discussion" for the rationale.
Proposed new [[Java]] page ''NOT finished yet!'''. See this "discussion" for the rationale.


<div class="messagebox" style="float: right; margin-left: 10px;">__TOC__</div>


== Java ==
== Java ==


Java is composed of:  
Java is about:  
* Community https://www.jcp.org/
* Communities: the [https://www.jcp.org/ Java Comunity Process] to define the platform, but also [https://community.oracle.com/community/java/jug Java User Groups]
* Platform (JVM, JRE ...) https://en.wikipedia.org/wiki/Java_(software_platform)  
* Platforms (JVM, JRE ...) to run applications on PC, mobiles, embedded devices https://en.wikipedia.org/wiki/Java_(software_platform)  
* Programming language (Java is the most popular) https://en.wikipedia.org/wiki/Java_(programming_language)
* Programming languages (Java is the most popular, but there are Scala, Groovy, Clojure ...) https://en.wikipedia.org/wiki/Java_(programming_language)


If you came here because an application ask for Java (or JRE, JVM) to be installed: install {{package|Java}}
<pre>
sudo dnf install java
</pre>


If it still does not work or the application ask specifically for ''Oracle Java'': See here
What do you want to do:
* If you came here because an '''application ask for Java''' (or JRE, JVM) '''to be installed''', then simply install {{package|java-1.8.0-openjdk}}.
* If it still does not work:
** Install javafx and icedtea-web packages as well.
** Lastly, and if the application '''ask specifically for [http://www.oracle.com/technetwork/java/javase/index.html Oracle Java]''': See here [[#Oracle_version]].
* If '''you want to develop, code, on the Java Platform''': See [[User:Brunovernay/Java/Development]]. ('''Careful to change the link for production''')


If you want to develop, code on the Java Platform: See Development


=== JRE JDK JVM JSE ... ===


== JRE JDK SDK JVM OpenJDK ? ==
Some vocabulary, if you are lost:


* ''JVM'' Java Virtual Machine. It relates to the Java Platform. It is in the package {{package|Java}}. There are other implementations, notably Oracle, see ...
* '''JRE''' Java Runtime Environment. Required to run Java code and applications. Install {{package|java-1.8.0-openjdk}}.
* ''JRE'' Java Runtime Environment. Idem JVM.
* '''JVM''' Java Virtual Machine. Main component of the JRE.
* ''JDK'' Java Development Kit
* '''JDK''' Java Development Kit.  Required only for development, coding.
* ''SDK'' Software Development Kit
* '''SDK''' Software Development Kit. idem JDK
* ''OpenJDK''  
* '''JavaWS''' [https://en.wikipedia.org/wiki/Java_Web_Start Java Web Start] is a framework to start application from the Internet 
* '''JavaFX''' [https://en.wikipedia.org/wiki/JavaFX JavaFX] is a plateform to create and deliver desktop and Rich Internet Apps.
* '''OpenJFX''' is the JavaFX Open Source implementation
* '''OpenJDK''' Open Source project behind the Java Platform http://openjdk.java.net/.
* '''IcedTea''' is a support project for OpenJDK (concern only developers) http://icedtea.classpath.org/
* '''IcedTea-Web''' is the Java Web Start package (It contains only JavaWS, No Applets anymore.) Install to run '''JNPL''' files.
* '''Applets''' Obsolete techno. Not implemented in any recent package.
* '''JSE''', '''J2SE''', '''JEE''' ... obsolete acronyms for '''J'''ava '''S'''tandard & '''E'''nterprise '''E'''dition.  ''JavaSE'' is like ''JRE''.


=== What is in Java OpenJDK package ===


For most users, it is just another system library. It is not an application with a GUI, but it is required by some other applications to run.
You might see a ''OpenJDK Policy tool'' desktop application that comes with the package, but you should not have to use it.
Beware that JavaFX and JavaWS are packaged separately!
== Multiple implementations ==
Fedora provides the Free {{package|java-1.8.0-openjdk}}. If this Open Source stack does not fulfil your requirements. Alternatives can be installed alongside or separately.
The '''J'''ava '''C'''ommunity '''P'''rocess defines the specifications of the platform that many implements (IBM J9, Jikes, Zing, Zulu Dalvik ...). We will only focus on Oracle here.
Multiple implementations can be installed side-by-side without interfering:
* The [[alternatives system]] allows to switch from one to another.
* An application can directly reference a specific Java installation
* Some applications include a java platform, it is then transparent for the user. (But the package is bigger.)


=== Oracle version ===
=== Oracle version ===


Some applications still ask for Oracle's implementation.  It is mostly based on the OpenJDK Open Source project, but there is proprietary code and Fedora does not package non-free software.
Installing Oracle Java is fine. Just beware '''not''' to use Oracle '''RPM''', as it will kill OpenJDK default packages!
Oracle provides a tarball: https://java.com/en/download/help/linux_x64_install.xml
We recommend to simply unpack the archives (tarball) to your home folder and set to path if necessary.
=== Switching alternatives ===
If you installed multiple Java implementations or version, you can configure your system to use one or another.
'''Developers''': beware that javac has its own independent alternative. i.e. to change the JDK, use ''alternatives ... javac''!
Switching is done using the [[alternatives system]] (''also used to change some other subsystems''). Java's subsystem name is surprisingly ''java'' and typical commands include:
<pre># alternatives --display java</pre>
<pre># alternatives --config java</pre>
See alternative's own documentation for more information for usage and parts involved.
Should be noted that JRE implementations installed outside Fedora distribution, may not support alternatives and thus not be visible there. Then the symbolic links under directory ''/etc/alternatives'' must be manually fixed.
= Java packages in Fedora =
There are many aliases for OpenJDK package, see http://pkgs.fedoraproject.org/cgit/rpms/java-1.8.0-openjdk.git/tree/java-1.8.0-openjdk.spec or do "dnf repoquery --provides java-1.8.0-openjdk".
You can use any of the following names:
* java
* java-1.8.0
* java-1.8.0-openjdk
* java-openjdk
* jre
* jre-1.8.0
* jre-1.8.0-openjdk
* jre-openjdk
<pre>dnf install java-1.8.0-openjdk</pre> might be the most safe (until 1.8 is EOL.)
'''Note''' that Java Web Start ('''JavaWS''') and '''JavaFX''' are packaged separately 'icedtea-web' and 'javafx' respectively.
Typically, without JavaFX, you may have error like:
<pre>java -jar scram.jar   
Error: Could not find or load main class com.frequal.scram.designer.jfx.Main</pre>
<pre>dnf install icedtea-web javafx</pre>
= Communicate =
You can subscribe to [https://admin.fedoraproject.org/mailman/listinfo/java-devel java-devel list] or talk to us in [irc://irc.freenode.net/fedora-java #fedora-java] Freenode IRC channel. Read [[Communicate]]  page for more information.
= See Also =
* [[User:Brunovernay/Java/FAQ]]
* [[User:Brunovernay/Java/Troubleshooting]]
* [https://Ask.FedoraProject.org/en/questions/scope:all/sort:activity-desc/tags:java/page:1/ Ask Fedora about Java]
* [https://bugzilla.redhat.com/buglist.cgi?component=java-1.8.0-openjdk&product=Fedora&bug_status=NEW&bug_status=ASSIGNED&bug_status=MODIFIED&bug_status=ON_DEV&bug_status=ON_QA&order=bugs.votes,bugs.bug_id Java-1.8.0-OpenJDK bugs]


== Java packages in Fedora ==
* [[SIGs/Java]]


== Java Development ==
= References =
* [http://openjdk.java.net/ OpenJDK Home]
* [https://wiki.openjdk.java.net/ OpenJDK Wiki]
* [http://jpackage.org/ Jpackage.org]


== Reference ==
[[Category:Java]]
== Communication and help ==
[[Category:Language-specific_SIGs]]

Latest revision as of 19:28, 4 October 2017

Proposed new Java page NOT finished yet!'. See this "discussion" for the rationale.

Java

Java is about:


What do you want to do:

  • If you came here because an application ask for Java (or JRE, JVM) to be installed, then simply install java-1.8.0-openjdk.
  • If it still does not work:
    • Install javafx and icedtea-web packages as well.
    • Lastly, and if the application ask specifically for Oracle Java: See here #Oracle_version.
  • If you want to develop, code, on the Java Platform: See User:Brunovernay/Java/Development. (Careful to change the link for production)


JRE JDK JVM JSE ...

Some vocabulary, if you are lost:

  • JRE Java Runtime Environment. Required to run Java code and applications. Install java-1.8.0-openjdk.
  • JVM Java Virtual Machine. Main component of the JRE.
  • JDK Java Development Kit. Required only for development, coding.
  • SDK Software Development Kit. idem JDK
  • JavaWS Java Web Start is a framework to start application from the Internet
  • JavaFX JavaFX is a plateform to create and deliver desktop and Rich Internet Apps.
  • OpenJFX is the JavaFX Open Source implementation
  • OpenJDK Open Source project behind the Java Platform http://openjdk.java.net/.
  • IcedTea is a support project for OpenJDK (concern only developers) http://icedtea.classpath.org/
  • IcedTea-Web is the Java Web Start package (It contains only JavaWS, No Applets anymore.) Install to run JNPL files.
  • Applets Obsolete techno. Not implemented in any recent package.
  • JSE, J2SE, JEE ... obsolete acronyms for Java Standard & Enterprise Edition. JavaSE is like JRE.

What is in Java OpenJDK package

For most users, it is just another system library. It is not an application with a GUI, but it is required by some other applications to run. You might see a OpenJDK Policy tool desktop application that comes with the package, but you should not have to use it.

Beware that JavaFX and JavaWS are packaged separately!

Multiple implementations

Fedora provides the Free java-1.8.0-openjdk. If this Open Source stack does not fulfil your requirements. Alternatives can be installed alongside or separately.

The Java Community Process defines the specifications of the platform that many implements (IBM J9, Jikes, Zing, Zulu Dalvik ...). We will only focus on Oracle here.

Multiple implementations can be installed side-by-side without interfering:

  • The alternatives system allows to switch from one to another.
  • An application can directly reference a specific Java installation
  • Some applications include a java platform, it is then transparent for the user. (But the package is bigger.)

Oracle version

Some applications still ask for Oracle's implementation. It is mostly based on the OpenJDK Open Source project, but there is proprietary code and Fedora does not package non-free software.

Installing Oracle Java is fine. Just beware not to use Oracle RPM, as it will kill OpenJDK default packages!

Oracle provides a tarball: https://java.com/en/download/help/linux_x64_install.xml

We recommend to simply unpack the archives (tarball) to your home folder and set to path if necessary.

Switching alternatives

If you installed multiple Java implementations or version, you can configure your system to use one or another.

Developers: beware that javac has its own independent alternative. i.e. to change the JDK, use alternatives ... javac!

Switching is done using the alternatives system (also used to change some other subsystems). Java's subsystem name is surprisingly java and typical commands include: 

# alternatives --display java
# alternatives --config java

See alternative's own documentation for more information for usage and parts involved.

Should be noted that JRE implementations installed outside Fedora distribution, may not support alternatives and thus not be visible there. Then the symbolic links under directory /etc/alternatives must be manually fixed.

Java packages in Fedora

There are many aliases for OpenJDK package, see http://pkgs.fedoraproject.org/cgit/rpms/java-1.8.0-openjdk.git/tree/java-1.8.0-openjdk.spec or do "dnf repoquery --provides java-1.8.0-openjdk".

You can use any of the following names:

  • java
  • java-1.8.0
  • java-1.8.0-openjdk
  • java-openjdk
  • jre
  • jre-1.8.0
  • jre-1.8.0-openjdk
  • jre-openjdk


dnf install java-1.8.0-openjdk

might be the most safe (until 1.8 is EOL.)


Note that Java Web Start (JavaWS) and JavaFX are packaged separately 'icedtea-web' and 'javafx' respectively.

Typically, without JavaFX, you may have error like: 

java -jar scram.jar    
Error: Could not find or load main class com.frequal.scram.designer.jfx.Main
dnf install icedtea-web javafx

Communicate

You can subscribe to java-devel list or talk to us in #fedora-java Freenode IRC channel. Read Communicate page for more information.

See Also


References

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