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1<?xml version='1.0'?> 1<?xml version="1.0" encoding="UTF-8"?>
2<?xml-stylesheet href="/xsl/guide.xsl" type="text/xsl"?> 2<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/java.xml,v 1.24 2006/06/24 19:06:34 nightmorph Exp $ -->
3<guide> 3<!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4
5<guide link="/doc/en/java.xml">
4<title>Gentoo Java Guide</title> 6<title>Gentoo Java Guide</title>
7
5<author title="Author and Editor"> 8<author title="Author">
6<mail link="karltk@gentoo.org">Karl Trygve Kalleberg</mail> 9 <mail link="karltk@gentoo.org">Karl Trygve Kalleberg</mail>
7</author> 10</author>
11<author title="Author">
12 <mail link="nichoj@gentoo.org">Joshua Nichols</mail>
13</author>
14<author title="Editor">
15 <mail link="nightmorph@gentoo.org">Joshua Saddler</mail>
16</author>
8 17
9<abstract> 18<abstract>
10Users' and Developers' Guide to Java in Gentoo 19This guide will introduce you to Java and explain how to use Java with Gentoo
20Linux.
11</abstract> 21</abstract>
12 22
23<!-- The content of this document is licensed under the CC-BY-SA license -->
24<!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
25<license/>
26
13<version>0.1.1</version> 27<version>0.4</version>
14<date>June 25, 2002</date> 28<date>2006-06-24</date>
15 29
16<chapter> 30<chapter>
17 31<title>What is Java?</title>
18<title>Installing a JDK/JRE</title>
19<section> 32<section>
20<title>Overview</title> 33<title>Overview</title>
21<body> 34<body>
22<p>Gentoo provides numerous JDKs and JREs. The default is the
23Blackdown JDK/JRE pair, as it is freely (beer) available without any
24registration fuss.</p>
25 35
26<note>As kaffe becomes a JRE/JDK drop-in replacement, that will most 36<p>
27likely become our default.</note> 37Java is a programming language developed by engineers of Sun Microsystems. The
38language is object-oriented and designed to run on multiple platforms without
39the need of recompiling code for each platform. Although Java can be compiled
40as a native program, much of Java's popularity can be attributed to its
41portability, along with other features such as garbage collection. To make
42platform independence possible the Java compiler compiles the Java code to an
43intermediate representation called "Java bytecode" that runs on a JRE (Java
44Runtime Environment) and not directly on the operating system.
45</p>
28 46
29<p>Both the Sun JDK/JRE and the IBM JDK/JRE are generally faster, but 47<p>
30getting them is a bit more work, as you are required to read and 48In order to run Java bytecode, one needs to have a JRE (Java Runtime
31accept their license before downloading (IBM additionally requires you 49Environment) installed. A JRE provides core libraries, a platform dependent
32to register).</p> 50Java Virtual Machine, plug-ins for browsers, among other things. A JDK (Java
51Development Kit) adds programming tools, such as a bytecode compiler and a
52debugger.
53</p>
33 54
34<p>Our ebuilds for the Sun and IBM JDK/JREs will notify you of where
35to go to download them.</p>
36</body> 55</body>
37</section>
38
39<section> 56</section>
40<title>Installing the Sun/IBM JDK/JREs</title> 57</chapter>
58
59<chapter>
60<title>Installing a JRE/JDK</title>
61<section>
62<title>The choices</title>
63<body>
64
65<p>
66Gentoo provides numerous JREs and JDKs. Among the current alternatives, we
67have:
68</p>
69
70<table>
71<tr>
72 <th>Vendor</th>
73 <th>JDK</th>
74 <th>JRE</th>
75</tr>
76<tr>
77 <ti>The Blackdown Java Kit</ti>
78 <ti>dev-java/backdown-jdk</ti>
79 <ti>dev-java/blackdown-jre</ti>
80</tr>
81<tr>
82 <ti>Sun's Java Kit</ti>
83 <ti>dev-java/sun-jdk</ti>
84 <ti>dev-java/sun-jre-bin</ti>
85</tr>
86<tr>
87 <ti>The IBM Java Kit</ti>
88 <ti>dev-java/ibm-jdk-bin</ti>
89 <ti>dev-java/ibm-jre-bin</ti>
90</tr>
91<tr>
92 <ti>The Compaq Java Kit for Alpha/Linux/GNU</ti>
93 <ti>dev-java/compaq-jdk</ti>
94 <ti>dev-java/compaq-jre</ti>
95</tr>
96<tr>
97 <ti>BEA WebLogic's J2SE Development Kit</ti>
98 <ti>dev-java/jrockit-jdk-bin</ti>
99</tr>
100</table>
101
102<!--
103TODO: list free implmentations?
104note about not drop-in replacemenets
105kaffe/sablevm/gcj/jamvm
106-->
107
108<p>
109The default is Blackdown for both the JRE and the JDK, as it is freely ("free
110as in beer") available without any registration fuss.
111</p>
112
113<p>
114Both the Sun and the IBM are generally faster, but getting them is a bit more
115hassle, as you are required to read and accept their license before downloading
116(IBM additionally requires you to register).
117</p>
118
119<p>
120Our ebuilds for the Sun and IBM JRE/JDKs will inform you how to download the
121appropriate files.
122</p>
123
41<body> 124</body>
125</section>
126<section>
127<title>Installing a JRE/JDKs</title>
128<body>
129
130<p>
131To install your profile's default JDK, you can run <c>emerge virtual/jdk</c>.
132Or to install your profile's default JRE, you can <c>emerge virtual/jre</c>.
133</p>
134
135<note>
136A JDK also includes a JRE, so if you install a JDK you shouldn't have to also
137have to install a JRE.
138</note>
139
140</body>
141</section>
142<section>
143<title>Installing the Sun/IBM JRE/JDKs</title>
144<body>
145
146<p>
42<p>If you run <c>emerge dev-java/sun-jdk-1.3.1</c> or <c>emerge 147If you run <c>emerge dev-java/sun-jdk</c> or <c>emerge
43dev-java/ibm-jdk-1.3.1</c>, you will be notified that you are required 148dev-java/ibm-jdk-bin</c>, you will be notified that you are required to
44to download the actual tarballs yourself. This has to do with license 149download the actual files yourself. This has to do with license restrictions
45restrictions for the Sun JDK/JRE (online click-wrap license) and 150for the Sun JRE/JDK (online click-wrap license) and registration issues with
46registration issues with the IBM JDK/JRE.</p> 151the IBM JRE/JDK.
152</p>
47 153
48<note>There is also a dev-java/sun-jdk-1.4.0, but not all packages 154<p>
49work nicely with Java 1.4, so you're on your own if you use the 1.4.0
50JDK.</note>
51
52<p>You should download the indicated file(s) into 155You should download the indicated file(s) into
53<path>/usr/portage/distfiles</path>. Once that is done, you can rerun 156<path>/usr/portage/distfiles</path>. Once there, you can rerun the emerge
54the emerge command, then the JDK/JRE will be installed properly into 157command, at which point the JRE/JDK will be begin to install.
55<path>/opt</path>.</p> 158</p>
56</body>
57</section>
58</chapter>
59 159
160</body>
161</section>
60<chapter> 162</chapter>
163
164<chapter>
61<title>Configuring your JDK/JRE</title> 165<title>Configuring your JRE/JDK</title>
62<section> 166<section>
63<title>Overview</title> 167<title>Overview</title>
64<body> 168<body>
169
170<p>
65<p>Gentoo has the ability to have multiple JDKs and JREs installed 171Gentoo has the ability to have multiple JDKs and JREs installed without causing
66without them conflicting. There are a few caveats to this, as noted 172conflicts.
67below.</p> 173</p>
68 174
175<p>
69<p>Using the <c>java-config</c> tool, you can set the system-wide 176Using the <c>java-config</c> tool, you can set the system-wide default
70default if you have root access. Users can also use <c>java-config</c> 177(provided you have root access). Users can also use <c>java-config</c> to set
71to set up their own personal default, that is different from the 178up their own personal default.
72system-wide default.</p> 179</p>
73</body>
74</section>
75 180
181<note>
182You can also use <e>eselect</e> to change the system and user vm. See
183<c>eselect java-vm help</c>.
184</note>
185
186</body>
76<section> 187</section>
188<section>
77<title>Setting a default JDK/JRE</title> 189<title>Setting a default JRE/JDK</title>
78<body> 190<body>
191
192<p>
79<p>Running the command <c>java-config --list-available-vms</c> will 193Running the command <c>java-config --list-available-vms</c> will give you a
80give you a list of all availble JREs and JDKs on your system, thus:</p> 194list of all JREs and JDKs installed on your system. Here is an example of
195output:
196</p>
197
198<pre caption="Listing available VMs">
199# <i>java-config --list-available-vms</i>
2001) Blackdown JDK 1.3.1 [blackdown-jdk-1.3] (/etc/env.d/java/20blackdown-jdk-1.3)
2012) Blackdown JDK 1.4.2.02 [blackdown-jdk-1.4] (/etc/env.d/java/20blackdown-jdk-1.4)
2023) Blackdown JRE 1.4.2.02 [blackdown-jre-1.4] (/etc/env.d/java/20blackdown-jre-1.4)
2034) IBM JDK 1.4.2 [ibm-jdk-bin-1.4] (/etc/env.d/java/20ibm-jdk-bin-1.4)
2045) IBM JRE 1.4.2 [ibm-jre-bin-1.4] (/etc/env.d/java/20ibm-jre-bin-1.4)
2056) WebLogic JRockit 1.4.2.05 [jrockit-jdk-bin-1.4] (/etc/env.d/java/20jrockit-jdk-bin-1.4)
2067) WebLogic JRockit 1.5.0.03 [jrockit-jdk-bin-1.5] (/etc/env.d/java/20jrockit-jdk-bin-1.5)
2078) Sun JDK 1.3.1.13 [sun-jdk-1.3] (/etc/env.d/java/20sun-jdk-1.3)
2089) Sun JDK 1.4.2.09 [sun-jdk-1.4] (/etc/env.d/java/20sun-jdk-1.4)
209*) Sun JDK 1.5.0.04 [sun-jdk-1.5] (/etc/env.d/java/20sun-jdk-1.5)
21011) Sun JRE 1.4.2.09 [sun-jre-bin-1.4] (/etc/env.d/java/20sun-jre-bin-1.4)
21112) Sun JRE 1.5.0.04 [sun-jre-bin-1.5] (/etc/env.d/java/20sun-jre-bin-1.5)
81<pre> 212</pre>
82[%1 ~] java-config --list-available-vms 213
83[blackdown-jdk-1.3.1] Blackdown JDK 1.3.1 (/etc/env.d/java/20blackdown-jdk-1.3.1) 214<p>
84[blackdown-jre-1.3.1] Blackdown JRE 1.3.1 (/etc/env.d/java/20blackdown-jre-1.3.1) 215The <e>*</e> indicates this is the current active vm (system-vm or user-vm when
85[ibm-jdk-1.3.0] IBM JDK 1.3.0 (/etc/env.d/java/20ibm-jdk-1.3.0)
86[ibm-jdk-1.3.1] IBM JDK 1.3.1 (/etc/env.d/java/20ibm-jdk-1.3.1)
87[ibm-jre-1.3.1] IBM JRE 1.3.1 (/etc/env.d/java/20ibm-jre-1.3.1)
88[sun-jdk-1.4.0] Sun JDK 1.4.0 (/etc/env.d/java/20sun-jdk-1.4.0)
89</pre>
90<p>The name in the brackets <path>"[]"</path> is the handle or ID for 216set). The name in the brackets (<e>[]</e>) is the handle or ID for that
91that particular VM. You use pass that ID to <c>java-config 217particular VM. You use the handle or the number to <c>java-config
92--set-system-vm</c>, thus:</p> 218--set-system-vm</c>. Here is an example of how to set the system VM.
219</p>
220
221<pre caption="Setting the System VM">
222<comment>(By handle (preferred))</comment>
223# <i>java-config --set-system-vm blackdown-jdk-1.4</i>
224<comment>(By number)</comment>
225# <i>java-config --set-system-vm 2</i>
93<pre> 226</pre>
94[#1 ~] java-config --set-system-vm=ibm-jdk-1.3.1
95Now using IBM JDK 1.3.1 (/etc/env.d/java/20ibm-jdk-1.3.1)
96</pre>
97 227
98<note>You will have to be root to run --set-system-vm</note>
99
100<p>Once you have issued <c>java-config --set-system-vm</c> with a
101particular VM ID, you will need to regenerate your /etc/profile.env,
102thus:</p>
103<pre> 228<p>
104[#1 ~] env-update
105</pre>
106
107<p>After this, you will either want to relogin, or resource
108<path>/etc/profile</path> into your environment.</p>
109
110<p>As a regular user, you can use <c>java-config --set-user-vm</c>, 229As a regular user, you can use <c>java-config --set-user-vm</c>.
111which will create <path>$HOME/.gentoo/java-env</path> with all 230</p>
112required env vars. You would normally source this from your shell's
113startup script (<path>$HOME/.zshenv</path> in my case).</p>
114</body>
115</section>
116 231
232<note>
233You no longer have to <c>source</c> the profile for updates to the user/system
234VM take place.
235</note>
236
237</body>
117<section> 238</section>
239<section id="preferred-vm">
240<title>Preferred VM</title>
241<body>
242
243<p>
244While merging Java packages, the VM can and will be switched as necessary.
245</p>
246
247<p>
248Because of the wide variety of available VMs, we do not have the resources to
249test and verify every package works on all of them. So to ensure that every
250packages merges smoothly, we have defined a list of <e>default/supported
251VMs</e> per arch. You can find them in
252<path>/usr/share/java-config/config/jdk-defaults.conf</path>. When you are
253merging a Java package, and it detects one of the VM in that file is installed,
254it will automatically use that VM, instead of the system-vm.
255</p>
256
257<p>
258The merge time VM switching is also needed when, for example, your system-vm is
259set a 1.4 VM and the package you are merging requires a 1.5 VM. While merging
260it will use the preferred 1.5 VM, leaving your system-vm choice intact.
261</p>
262
263<p>
264Of course, Gentoo is all about choice, so you can override these defaults in
265<path>/etc/java-config-2/build/jdk.conf</path> and have complete control over
266which VM will get used. Some examples:
267</p>
268
269<pre caption="Example /etc/java-config-2/build/jdk.conf">
270<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>
271*=sun-jdk
272</pre>
273
274<pre caption="Example /etc/java-config-2/build/jdk.conf">
275<comment>(Always use sun-jdk-1.5 wherever possible, except for when a 1.4 or 1.3 VM is explicitly required)</comment>
276*=sun-jdk-1.5
277</pre>
278
279<pre caption="Example /etc/java-config-2/build/jdk.conf">
280<comment># For 1.3 I prefer sun-jdk 1.4 but when it is not available, use ibm-jdk-bin,
281# For 1.4, use blackdown-jdk, and for 1.5, use sun-jdk </comment>
2821.3=sun-jdk-1.4 ibm-jdk-bin
2831.4=blackdown-jdk
2841.5=sun-jdk
285</pre>
286
287<warn>
288You do not have to edit this file. If you change these options to use a
289unsupported VM, things could possibly break. Bugs reported with a unsupported
290VM will a lower priority if they aren't present with supported VMs.
291</warn>
292
293</body>
294</section>
295</chapter>
296
297<chapter>
298<title>Compilers</title>
299<section>
300<body>
301
302<p>
303The standard Java compiler used for building is javac, which comes with each
304JDK. In addition to configuring the VM used at build time, it is also possible
305configure which compiler is used. Essentially, you define a list your
306preference for which compiler to use in
307<path>/etc/java-config-2/build/compilers.conf</path>.
308</p>
309
310<pre caption="/etc/java-config-2/build/compilers.conf">
311# If the ebuild supports it
312# it will check the COMPILERS var front to back and
313# use the first compiler that is installed
314
315COMPILERS="ecj-3.1 jikes javac"
316</pre>
317
318<p>
319Some compilers don't support all possible -target and -source arguments.
320Therefore, each compiler in the list is checked to see if it can support the
321desired -source/-target. javac will work in all cases, so if no other suitable
322compiler is found, it will be used instead.
323</p>
324
325<p>
326More details about each compiler are provided below:
327</p>
328
329<table>
330<tr>
331 <th>Name</th>
332 <th>Handle</th>
333 <th>Package</th>
334 <th>Description</th>
335</tr>
336<tr>
337 <ti>javac</ti>
338 <ti>javac</ti>
339 <ti>N/A</ti>
340 <ti>
341 This is the default compiler that will be used, and comes with each JDK.
342 </ti>
343</tr>
344<tr>
345 <ti>jikes</ti>
346 <ti>jikes</ti>
347 <ti>dev-java/jikes</ti>
348 <ti>
349 Jikes was originally developed by IBM. Anecdotally, it is generally quicker
350 than javac. Note however, that it is more pedantic, and will fail under a
351 few circumstances where javac has no issue. It also does not support Java
352 1.5 syntax yet.
353 </ti>
354</tr>
355<tr>
356 <ti>Eclipse Compiler for Java</ti>
357 <ti>ecj-3.1</ti>
358 <ti>=dev-java/eclipse-ecj-3.1*</ti>
359 <ti>
360 ECJ is the compiler used by the Eclipse software development kit. It is
361 very full featured, and is pretty fast. It does support Java 1.5 syntax.
362 </ti>
363</tr>
364</table>
365
366</body>
367</section>
368</chapter>
369
370<chapter>
118<title>Setting a default CLASSPATH</title> 371<title>Setting a default CLASSPATH</title>
372<section>
119<body> 373<body>
374
375<warn>
376The options explained in this section should be considered deprecated and will
377be most likely be removed in the future. We strongly recommend against using
378these, because your Java projects or application should ideally manage their
379own classpaths. If you choose to specify a default CLASSPATH, some applications
380may behave unexpectedly, because classes they weren't expecting would be on the
381classpath.
382</warn>
383
384<p>
120<p><c>java-config</c> can also be used to set a system-wide default 385<c>java-config</c> can also be used to set a system-wide default CLASSPATH, as
121CLASSPATH, and of course a user-specific default CLASSPATH.</p> 386well a user-specific default CLASSPATH.
387</p>
122 388
123<p>First you want to list available java libraries that might be 389<p>
124interesting to put in your CLASSPATH, thus:</p> 390First, you will want to list available Java libraries installed on your system
391that might want to be put in your CLASSPATH. Here is an example of output:
392</p>
393
394<pre caption="Listing classes">
395# <i>java-config --list-available-packages</i>
396[xerces-2] The next generation of high performance, fully compliant XML parsers in the Apache Xerces family (/usr/share/xerces-2/package.env)
397[junit] Simple framework to write repeatable tests (/usr/share/junit/package.env)
398[bsh] BeanShell: A small embeddable Java source interpreter (/usr/share/bsh/package.env)
399[bcel] The Byte Code Engineering Library: analyze, create, manipulate Java class files (/usr/share/bcel/package.env)
400[log4j] A low-overhead robust logging package for Java (/usr/share/log4j/package.env)
401...
125<pre> 402</pre>
126[%1 ~] java-config --list-available-packages 403
127[ant] No description (/usr/share/ant/classpath.env) 404<p>
128[java-gnome] No description (/usr/share/java-gnome/classpath.env) 405Again, the names in brackets (<e>[]</e>) are the IDs that you have to pass to
129[java-gtk] No description (/usr/share/java-gtk/classpath.env) 406<c>java-config --set-system-classpath</c>. Here is an example:
130[log4j] "" (/usr/share/log4j/package.env)
131</pre> 407</p>
132 408
133<note>None of these packages have a proper description. That is 409<pre caption="Setting classpaths">
134something that will be implemented in the not-so-distant 410# <i>java-config --set-system-classpath log4j,xerces-2</i>
135future.</note>
136
137<p>Again, the name in brackets <path>"[]"</path> are the IDs that you
138have to pass to <c>java-config --set-system-classpath</c>, thus:</p>
139<pre> 411</pre>
140java-config --set-system-classpath=log4j,java-gtk,java-gnome 412
141</pre> 413<note>
142<note>The current directory (.) will not be part of the system classpath, 414The current directory (<path>.</path>) will not be part of the system
143as that should be added in root's login profile.</note> 415classpath, as that should be added in your system's login profile.
144<p>Again, you will want to run <c>env-update</c> to update your 416</note>
145system's environment, and you might also want to relogin or resource 417
418<p>
419You will have to update your environment by relogging in or sourcing
146the <path>/etc/profile</path>.</p> 420<path>/etc/profile</path>.
421</p>
422
423<p>
147<p>For users, <c>java-config --set-user-classpath</c> will create 424For users, <c>java-config --set-user-classpath</c> will create
148<path>$HOME/.gentoo/java-env-classpath</path>, which is automatically 425<path>~/.gentoo/java-env-classpath</path>, which you should then source from
149included by <path>$HOME/.gentoo/java-env</path>.</p> 426your shell's profile.
427</p>
428
429<pre caption="Sourcing user specific classpath">
430<i>if [[ -f "${HOME}/.gentoo/java-env-classpath" ]]; then
431 source ${HOME}/.gentoo/java-env-classpath
432fi</i>
433</pre>
434
435<p>
436If you really want a system wide or user default classpath you can add
437something like like the following to your shell's profile. But we would advise
438against it.
439</p>
440
441<pre caption="Setting classpath">
442# <i>export CLASSPATH="${CLASSPATH}:$(java-config --classpath log4j,xerces-2)"</i>
443</pre>
444
445</body>
446</section>
447</chapter>
448
449<chapter>
450<title>USE flags for use with Java</title>
451<section>
452<title>Setting USE flags</title>
453<body>
454
455<p>
456For more information regarding USE flags, refer to the <uri
457link="/doc/en/handbook/handbook-x86.xml?part=2&amp;chap=2">USE flags</uri>
458chapter from the Gentoo Handbook.
459</p>
460
461</body>
462</section>
463<section>
464<title>The flags</title>
465<body>
466
467<ul>
468 <li>The <b>java</b> flag adds support for Java in a variety of programs</li>
469 <li>
470 The <b>nsplugin</b> flag adds support for Mozilla-like browsers (including
471 Firefox).You will need this for viewing Java applets in your Mozilla-like
472 browser.
473 </li>
474 <li>
475 The <b>doc</b> flag will typically install API documentation, as generated
476 by javadoc.
477 </li>
478 <li>
479 The <b>source</b> flag will install a zip of the package's source code.
480 This is typically used to provide your IDE with the source code for the
481 package.
482 </li>
483</ul>
484
150</body> 485</body>
151</section> 486</section>
152</chapter> 487</chapter>
153 488
154<chapter> 489<chapter>
155<title>Additional resources</title> 490<title>Additional resources</title>
156<section> 491<section>
157<title>Off-line resources</title> 492<title>Off-line resources</title>
158<body> 493<body>
494
159<ul> 495<ul>
160<li>java-config man page</li> 496 <li>java-config man page</li>
161<li><c>java-config --help</c></li> 497 <li><c>java-config --help</c></li>
162<li>The <path>/usr/bin/java-config</path> script itself</li>
163</ul> 498</ul>
499
164</body> 500</body>
165</section> 501</section>
166<section> 502<section>
167<title>Online resources</title> 503<title>Online resources</title>
168<body> 504<body>
505
169<ul> 506<ul>
170<li>The <uri link="http://lists.gentoo.org/pipermail/gentoo-dev/"> 507 <li>
171gentoo-dev </uri>, 508 The <uri link="http://www.gentoo.org/proj/en/java/">Java Project
172<uri link="http://lists.gentoo.org/pipermail/gentoo-user/"> gentoo-user 509 Page</uri>
510 </li>
511 <li>
512 The <uri
513 link="http://news.gmane.org/gmane.linux.gentoo.java">gentoo-java</uri>,
514 <uri
515 link="http://news.gmane.org/gmane.linux.gentoo.user">gentoo-user</uri>, and
516 <uri
517 link="http://news.gmane.org/gmane.linux.gentoo.devel">gentoo-dev</uri>
173</uri> mailing list archives</li> 518 mailing list archives
174<li>#gentoo on irc.openprojects.net</li> 519 </li>
520 <li>#gentoo and #gentoo-java on irc.freenode.net</li>
521 <li>
522 <uri
523 link="http://en.wikipedia.org/wiki/Java_programming_language">Wikipedia's
524 entry for Java</uri>
525 </li>
175</ul> 526</ul>
176</body>
177</section>
178</chapter>
179<chapter>
180<title>Caveats</title>
181<section>
182<title>General</title>
183<body>
184<p>If you select a JRE as your default VM, you may not have a
185<c>javac</c> command handy at all times, unless you have manually
186installed a symlink to take care of that.</p>
187 527
188<p>Jikes will be used to compile some of the largest packages, if it
189is available. With time, we hope to be able to compile all
190java-dependent packages with Jikes, so some dependencies on the JDK
191can be replaced with a dependency on the JRE.</p>
192
193<p>With some versions of Portage, doing an <c>emerge --world
194update</c> will install the JDK regardless if whether you have it
195installed before or not. This is a known bug addressed in later
196versions of Portage.</p>
197</body> 528</body>
198</section> 529</section>
199</chapter> 530</chapter>
200</guide> 531</guide>

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