<guide link="/doc/en/java-user.xml">

<guide link="/doc/en/java.xml">

<title>Gentoo Java User Guide</title>

<title>Gentoo Java Guide</title>

<version>0.1.8</version>

<version>0.4</version>

<date>2006-05-16</date>

<date>2006-06-24</date>

portability, along with other features such as garbage collection.

portability, along with other features such as garbage collection. To make

To make platform independence possible the Java compiler compiles the Java

platform independence possible the Java compiler compiles the Java code to an

code to an intermediate representation called "Java bytecode" that runs on a

intermediate representation called "Java bytecode" that runs on a JRE (Java

JRE (Java Runtime Environment) and not directly on the operating system.

Runtime Environment) and not directly on the operating system.  is a JRE for

is a JRE for each supported OS that runs natively on the OS.

each supported OS that runs natively on the OS.

The default is Blackdown for both the JRE and the JDK , as it is freely ("free as in beer")

The default is Blackdown for both the JRE and the JDK, as it is freely ("free

available without any registration fuss.

as in beer") available without any registration fuss.

Both the Sun and the IBM are generally faster, but getting them

Both the Sun and the IBM are generally faster, but getting them is a bit more

is a bit more hassle, as you are required to read and accept their license before

hassle, as you are required to read and accept their license before downloading

downloading (IBM additionally requires you to register).

(IBM additionally requires you to register).

Our ebuilds for the Sun and IBM JRE/JDKs will inform you how to download the appropriate files.

Our ebuilds for the Sun and IBM JRE/JDKs will inform you how to download the

appropriate files.

To install your profile's default JDK, you can run <c>emerge virtual/jdk</c>

To install your profile's default JDK, you can run <c>emerge virtual/jdk</c>.

. Or to install your profile's default JRE, you can <c>emerge virtual/jre</c>.

Or to install your profile's default JRE, you can <c>emerge virtual/jre</c>.

A JDK also includes a JRE, so if you install a JDK you shouldn't have to also 

A JDK also includes a JRE, so if you install a JDK you shouldn't have to also

<path>/usr/portage/distfiles</path>. Once there, you can rerun the

<path>/usr/portage/distfiles</path>. Once there, you can rerun the emerge

emerge command, at which point the JRE/JDK will be begin to install.

command, at which point the JRE/JDK will be begin to install.

Gentoo has the ability to have multiple JDKs and JREs installed without causing conflicts.

Gentoo has the ability to have multiple JDKs and JREs installed without causing

conflicts.

Using the <c>java-config</c> tool, you can set the system-wide default (provided you have 

Using the <c>java-config</c> tool, you can set the system-wide default

root access). Users can also use <c>java-config</c> to set up their own

(provided you have root access). Users can also use <c>java-config</c> to set

personal default.

up their own personal default.

The <e>*</e> indicated this is the current active vm (system-vm or user-vm when

The <e>*</e> indicates this is the current active vm (system-vm or user-vm when

set). The name in the brackets <e>"[]"</e> is the handle or ID for that

set). The name in the brackets (<e>[]</e>) is the handle or ID for that

<comment>By handle (preferred)</comment>

<comment>(By handle (preferred))</comment>

<comment>By number</comment>

<comment>(By number)</comment>

As a regular user, you can use <c>java-config --set-user-vm</c>

As a regular user, you can use <c>java-config --set-user-vm</c>.

You no longer have to <c>source</c> the profile for updates to the 

You no longer have to <c>source</c> the profile for updates to the user/system

user/system VM take place.

VM take place.

test and verify every package works on all of them.  So to ensure that every

test and verify every package works on all of them. So to ensure that every

packages merges smoothly, we have defined a list of <e>default / supported

packages merges smoothly, we have defined a list of <e>default/supported

vms</e> per arch. You can find them in

VMs</e> per arch. You can find them in

<path>/usr/share/java-config/config/jdk-defaults.conf</path>.  When you are

<path>/usr/share/java-config/config/jdk-defaults.conf</path>. When you are

set a 1.4 VM and the package you are merging requires a 1.5 VM.  While merging

set a 1.4 VM and the package you are merging requires a 1.5 VM. While merging

it will use the preferred 1.5 Vm, leaving your system-vm choice intact.

it will use the preferred 1.5 VM, leaving your system-vm choice intact.

<path>/etc/java-config-2/build/jdk.conf</path> and have complete control over which VM

<path>/etc/java-config-2/build/jdk.conf</path> and have complete control over

will get used.<br/>

which VM will get used. Some examples:

Some examples:

<comment># I Always want it to use a sun-jdk, ie sun-jdk-1.4 for 1.4, sun-jdk-1.5 for 1.5, etc</comment>

<comment>(I always want it to use a sun-jdk, ie sun-jdk-1.4 for 1.4, sun-jdk-1.5 for 1.5, etc)</comment>

<comment># Always use sun-jdk-1.5 wherever possible (except for when a 1.4 or 1.3 VM is explicitly required</comment>

<comment>(Always use sun-jdk-1.5 wherever possible, except for when a 1.4 or 1.3 VM is explicitly required)</comment>

You do not have to edit this file. If you change these options to use a 

You do not have to edit this file. If you change these options to use a

unsupported VM, things could possibly break. Bugs reported with a

unsupported VM, things could possibly break. Bugs reported with a unsupported

unsupported VM will a lower priority if they aren't present with supported VMs.

VM will a lower priority if they aren't present with supported VMs.

these, because your Java projects or application should ideally manage their own classpaths. If you choose to specify a default CLASSPATH, some applications may behave unexpectedly, because classes they weren't expecting would be on the classpath.

these, because your Java projects or application should ideally manage their

own classpaths. If you choose to specify a default CLASSPATH, some applications

may behave unexpectedly, because classes they weren't expecting would be on the

classpath.

<c>java-config</c> can also be used to set a system-wide default CLASSPATH, as well a user-specific default CLASSPATH.

<c>java-config</c> can also be used to set a system-wide default CLASSPATH, as

well a user-specific default CLASSPATH.

First, you will want to list available Java libraries installed on your system that might want to be put in your CLASSPATH.<br/>

First, you will want to list available Java libraries installed on your system

Here is an example of output:

that might want to be put in your CLASSPATH. Here is an example of output:

Again, the name in brackets <path>"[]"</path> are the IDs that you have to pass

Again, the names in brackets (<e>[]</e>) are the IDs that you have to pass to

to <c>java-config --set-system-classpath</c>.<br/>

<c>java-config --set-system-classpath</c>. Here is an example:

Here is an example:

The current directory (.) will not be part of the system classpath, as that

The current directory (<path>.</path>) will not be part of the system

should be added in your system's login profile.

classpath, as that should be added in your system's login profile.

    The <b>nsplugin</b> flag adds support for Mozilla-like browsers

    The <b>nsplugin</b> flag adds support for Mozilla-like browsers (including

    (including Firefox).You will need this for viewing Java applets in your

    Firefox).You will need this for viewing Java applets in your Mozilla-like

    Mozilla-like browser.

    browser.

  </li>

  <li>

    The <b>doc</b> flag will typically install API documentation, as generated

    by javadoc.

  </li>

  <li>

    The <b>source</b> flag will install a zip of the package's source code.

    This is typicall used to provide your IDE with the source code for the

    package.

    The 

    The <uri link="http://www.gentoo.org/proj/en/java/">Java Project

    <uri link="http://news.gmane.org/gmane.linux.gentoo.java">gentoo-java</uri>,

    Page</uri>

    <uri link="http://news.gmane.org/gmane.linux.gentoo.user">gentoo-user</uri>,

  </li>

  <li>

    The <uri

    link="http://news.gmane.org/gmane.linux.gentoo.java">gentoo-java</uri>,

    <uri

    link="http://news.gmane.org/gmane.linux.gentoo.user">gentoo-user</uri>,

    <uri link="http://en.wikipedia.org/wiki/Java_programming_language">Wikipedia's entry for Java</uri>

    <uri

    link="http://en.wikipedia.org/wiki/Java_programming_language">Wikipedia's

    entry for Java</uri>