# Java

Related articles

- Java Package Guidelines
- Java Runtime Environment Fonts

From the Wikipedia article:

  Java is a programming language originally developed by Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of computer architecture.

Arch Linux officially supports the open source OpenJDK versions 7 and 8. All these JVM can be installed without conflict and switched between using helper script `archlinux-java`. Several other Java environments are available in AUR but are not officially supported.

## Installation

Note: Installing a JDK will automatically pull its JRE dependency.
Note: After installation, the Java environment will need to be recognized by the shell (`$PATH` variable). This can be done by sourcing `/etc/profile` from the command line or by logging out/in again of a Desktop Environment.

Two common packages named java-runtime-common and java-environment-common are automatically pulled as dependency and provide environment file `/etc/profile.d/jre.sh`. This file contains all JVM common environment variables. Package java-runtime-common also provides a utility script `archlinux-java` that can display and change the default Java environment. This script sets links `/usr/lib/jvm/default` and `/usr/lib/jvm/default-runtime` to point at a valid non-conflicting Java environment installed and Java runtime in `/usr/lib/jvm/java-${JAVA_MAJOR_VERSION}-${VENDOR_NAME`}. Most executables provided by the Java environment set have direct links from `/usr/bin`, others are available in `$PATH`.

Warning: File `/etc/profile.d/jdk.sh` is not provided any more by any package.

The following packages are available in the official repositories:

### OpenJDK 7

Package name | Use
--- | ---
jre7-openjdk-headless | Java runtime environment (JRE) without any graphical tool - version 7
jre7-openjdk | Complete Java Runtime Environment (JRE) - version 7
jdk7-openjdk | Java Development Kit (JDK) - version 7
openjdk7-doc | OpenJDK javadoc - version 7
openjdk7-src | OpenJDK sources - version 7

### OpenJDK 8

Package name | Use
--- | ---
jre8-openjdk-headless | Java runtime environment (JRE) without any graphical tool - version 8
jre8-openjdk | Complete Java Runtime Environment (JRE) - version 8
jdk8-openjdk | Java Development Kit (JDK) - version 8
openjdk8-doc | OpenJDK javadoc - version 8
openjdk8-src | OpenJDK sources - version 8

### OpenJFX

JavaFX is also available from the official repositories. It requires the OpenJDK 8.

Package name | Use
--- | ---
java-openjfx | Java OpenJFX 8 client application platform (open-source implementation of JavaFX)
java-openjfx-doc | OpenJFX javadoc
java-openjfx-src | OpenJFX sources

## Flagging packages as out-of-date

Although the Arch Linux package releases may contain a reference to the proprietary versions the packages are based on, the open-source project has its own versioning scheme:

- jre7-openjdk, jdk7-openjdk, and jre7-openjdk-headless should be flagged as out-of-date based on the IcedTea version (e.g. `2.4.3`), rather than on the Oracle reference version (e.g. `u45` in the release `7.u45_2.4.3-1`).
- icedtea-web should be flagged as out-of-date based on the IcedTea Web version (e.g. `1.4.1`). This is independent of the IcedTea version.

## Switching between JVM

The helper script `archlinux-java` provides such functionalities:

    archlinux-java <COMMAND>

    COMMAND:
    	status		List installed Java environments and enabled one
    	get		Return the short name of the Java environment set as default
    	set <JAVA_ENV>	Force <JAVA_ENV> as default
    	unset		Unset current default Java environment
    	fix		Fix an invalid/broken default Java environment configuration

### List compatible Java environments installed

    $ archlinux-java status

Example:

    $ archlinux-java status
    Available Java environments:
      java-7-openjdk (default)
      java-8-openjdk/jre

Note the (default) denoting that `java-7-openjdk` is currently set as default. Invocation of `java` and other binaries will rely on this Java install. Also note on the previous output that only the JRE part of OpenJDK 8 is installed here.

### Change default Java environment

    # archlinux-java set <JAVA_ENV_NAME>

Example:

    # archlinux-java set java-8-openjdk/jre

Tip: To see possible `<JAVA_ENV_NAME>` names, use `archlinux-java status`.

Note that `archlinux-java` will not let you set an invalid Java environment. In the previous example, jre8-openjdk is installed but jdk8-openjdk is not so trying to set `java-8-openjdk` will fail:

    # archlinux-java set java-8-openjdk
    '/usr/lib/jvm/java-8-openjdk' is not a valid Java environment path

### Unsetting the default Java environment

There should be no need to unset a Java environment as packages providing them should take care of this. Still should you want to do so, just use command `unset`:

    # archlinux-java unset

### Fixing the default Java environment

If an invalid Java environment link is set, calling the `archlinux-java fix` command tries to fix these. Also note that if no default Java environment is set, this will look for valid ones and try to set it for you. Officially supported packages "OpenJDK 7" and "OpenJDK 8" will be considered first in this order, then un-official packages from AUR.

    # archlinux-java fix

### Launching an application with the non-default java version

If you want to launch an application with another version of java than the default one (for example if you have both version jre7 and jre8 installed on your system), you can wrap your application in a small bash script to locally change the default PATH of java. For example if the default version is jre7 and you want use jre8:

    #!/bin/sh

    export PATH=/usr/lib/jvm/java-8-openjdk/jre/bin/:$PATH
    exec /path/to/application "$@"

## Package pre-requisites to support `archlinux-java`

This section is targeted at packager willing to provide packages in AUR for an alternate JVM and be able to integrate with Arch Linux JVM scheme to use `archlinux-java`. To do so, packages should:

- Place all files under `/usr/lib/jvm/java-${JAVA_MAJOR_VERSION}-${VENDOR_NAME}`
- Ensure all executables for which java-runtime-common and java-environment-common provide links are available in the corresponding package
- Ship links from `/usr/bin` to executables, only if these links do not already belong to java-runtime-common and java-environment-common
- Suffix man pages with `-${VENDOR_NAME}${JAVA_MAJOR_VERSION}` to prevent conflicts (see jre8-openjdk file list where man pages are suffixed with `-openjdk8`)
- Do not declare any conflicts nor replaces with other JDKs, `java-runtime`, `java-runtime-headless` nor `java-environment`
- Use script `archlinux-java` in install functions to set the Java environment as default if no other valid Java environment is already set (ie: package should not force install as default). See officially supported Java environment package sources for examples

Also please note that:

- Packages that need any Java environment should declare dependency on `java-runtime`, `java-runtime-headless` or `java-environment` as usual
- Packages that need a specific Java vendor should declare dependency on the corresponding package
- OpenJDK packages now declare `provides="java-runtime-openjdk=${pkgver}"` etc. This enables a third-party package to declare dependency on an OpenJDK without specifying a version

## Unsupported JVM from AUR

Warning: Packages in AUR may or may not support `archlinux-java`

### Java SE

Several packages from AUR provide Oracle's implementations of JRE and JDK, but the main ones are jreAUR, server-jreAUR and jdkAUR.

#### Java SE 9

The development version of Java 9 includes jre-develAUR and jdk-develAUR.

#### Java SE 6/7

Older versions include jre6AUR/jre7AUR and jdk6AUR/jdk7AUR.

#### 32-bit Java SE

Almost all of the above packages can be found in 32-bit by prefixing `bin32-`, e.g. bin32-jreAUR and bin32-jdkAUR.

Note: These packages use `archlinux-java32` (java32-runtime-commonAUR), which is separate from `archlinux-java` (java-runtime-common), but functions the same, by suffixing the Java links with `32`, e.g. `java32`.

### VMkit

VMkit is an LLVM-based framework for JIT virtual machines. J3 is a JVM running on VMkit. The webpage can be found here: vmkit. J3 depends on the GNU classpath libraries, but may also work with the Apache class path libraries.

### Parrot VM

Parrot is a VM that offers experimental support for Java through two different methods: Either as a Java VM bytecode translator or as a Java compiler targeting the Parrot VM. Install it with the parrot package.

## Troubleshooting

### MySQL

Due to the fact that the JDBC-drivers often use the port in the URL to establish a connection to the database, it is considered "remote" (i.e., MySQL does not listen to the port as per its default settings) despite the fact that they are possibly running on the same host, Thus, to use JDBC and MySQL you should enable remote access to MySQL, following the instructions in MySQL#Grant remote access.

### Impersonate another window manager

You may use the wmname from suckless.org to make the JVM believe you are running a different window manager. This may solve a rendering issue of Java GUIs occurring in window managers like Awesome or Dwm or Ratpoison.

    $ wmname LG3D

You must restart the application in question after issuing the wmname command.

This works because the JVM contains a hard-coded list of known, non-re-parenting window managers. For maximum irony, some users prefer to impersonate `LG3D`, the non-re-parenting window manager written by Sun, in Java.

### Illegible fonts

In addition to the suggestions mentioned below in #Better font rendering, some fonts may still not be legible afterwards. If this is the case, there is a good chance Microsoft fonts are being used. Install ttf-ms-fontsAUR from the AUR.

### Missing text in some applications

If some applications are completely missing texts it may help to use the options under #Tips and tricks as suggested in FS#40871.

### Applications not resizing with WM, menus immediately closing

The standard Java GUI toolkit has a hard-coded list of "non-reparenting" window managers. If using one that is not on that list, there can be some problems with running some Java applications. One of the most common problems is "gray blobs", when the Java application renders as a plain gray box instead of rendering the GUI. Another one might be menus responding to your click, but closing immediately.

There are several things that may help:

- For jre7-openjdk or jre8-openjdk, append the line `export _JAVA_AWT_WM_NONREPARENTING=1` in `/etc/profile.d/jre.sh`. Then, source the file `/etc/profile.d/jre.sh` or log out and log back in.
- For Oracle's JRE/JDK, use SetWMName. However, its effect may be canceled when also using `XMonad.Hooks.EwmhDesktops`. In this case, appending

     >> setWMName "LG3D"

to the `LogHook` may help.

See [1] for more information.

### System freezes when debugging JavaFX Applications

If your system freezes while debugging a JavaFX Application, you can try to supply the JVM option `-Dsun.awt.disablegrab=true`.

See http://bugs.java.com/view_bug.do?bug_id=6714678

## Tips and tricks

Note: Suggestions in this section are applicable to all applications, using explicitly installed (external) Java runtime. Some applications are bundled with own (private) runtime or use own mechanics for GUI, font rendering, etc., so none of written below is guaranteed to work.

Behavior of most Java applications can be controlled by supplying predefined variables to Java runtime. From this forum post, a way to do it consists of adding the following line in your `~/.bashrc` (or `/etc/profile.d/jre.sh` to affect programs that are not run by sourcing `~/.bashrc`, e.g., launching a program from Gnome's Applications view):

    export _JAVA_OPTIONS="-D<option 1> -D<option 2>..."

For example, to use system anti-aliased fonts and make swing use the GTK look and feel:

    export _JAVA_OPTIONS='-Dawt.useSystemAAFontSettings=on -Dswing.aatext=true -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel'

### Better font rendering

Both closed source and open source implementations of Java are known to have improperly implemented anti-aliasing of fonts. This can be fixed with the following options: `-Dawt.useSystemAAFontSettings=on`, `-Dswing.aatext=true`

See Java Runtime Environment fonts for more detailed information.

### Silence 'Picked up _JAVA_OPTIONS' message on command line

Setting the _JAVA_OPTIONS environment variables makes java (openjdk) write to stderr messages of the form: 'Picked up _JAVA_OPTIONS=...'. To supress those mesages in your terminal you can unset the environment variable in your shell startup files and alias java to pass those same options as command line arguments:

     _SILENT_JAVA_OPTIONS="$_JAVA_OPTIONS"
     unset _JAVA_OPTIONS
     alias java='java "$_SILENT_JAVA_OPTIONS"'

### GTK LookAndFeel

If your Java programs look ugly, you may want to set up the default look and feel for the swing components:

`swing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel`.

Some Java programs insist on using the cross platform Metal look and feel. In some of these cases you can force these apps to use the GTK look and feel by setting the following property:

`swing.crossplatformlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel`.

Note: Forcing Java to use GTK may break some applications. Currently JRE/JDK (as of 8u60) is linked against GTK2 while many desktop applications start using GTK3. If a GTK3 app has Java plugins with GUI, the app is likely to crash when opening the Java GUI, as mixing GTK2 and GTK3 in the same process is not supported. Libreoffice 5.0 is an example for this.

### Non-reparenting window managers

Non-reparenting window managers user should set the following environment variable in their `.xinitrc`

     export _JAVA_AWT_WM_NONREPARENTING=1

## See also

- Introduction to Programming Using Java

Category:

- Programming languages