[doc] Update docs, remove toolchain requirements, require java 9

BUILDING.md

@@ -1,11 +1,7 @@
 # How to build PMD
 
-PMD uses [Maven](https://maven.apache.org/).
-
-You'll need to have a `~/.m2/toolchains.xml` file setup
-with jdk 1.7 and jdk 1.8 (for some features in pmd).
-See [maven toolchains](https://maven.apache.org/guides/mini/guide-using-toolchains.html).
-A example file can be found here: [example-toolchains.xml](https://github.com/pmd/pmd/blob/master/example-toolchains.xml).
+PMD uses [Maven](https://maven.apache.org/) and requires [Java 9](http://www.oracle.com/technetwork/java/javase/downloads/index.html)
+for building.
 
 PMD uses the [maven wrapper](https://github.com/takari/maven-wrapper), so you can simply build PMD as following:
 
@@ -19,11 +15,14 @@ This will create the zip files in the directory `pmd-dist/target`:
 
 That's all !
 
-## How to build the documentation (maven site)?
+**Note:** While Java 9 is required for building, running PMD only requires Java 7 (or Java 8 for Apex).
+
+## How to build the documentation?
 
-Building the maven site is done with the following commands:
+    cd docs
+    bundle install # once
+    bundle exec jekyll build
 
-    ./mvnw clean install -DskipTests=true
-    ./mvnw install site site:stage -Psite
+You'll find the built site in the directory `_site/`.
 
-You'll find the built site in the directory `target/staging/`.
+For more info, see [README in docs directory](docs/README.md).

docs/pages/pmd/devdocs/building.md

@@ -6,32 +6,34 @@ author: Tom Copeland, Xavier Le Vourch <xlv@users.sourceforge.net>
 
 # Compiling PMD
 
-*   JDK 1.7 or higher
+*   JDK 9 or higher
 *   [Apache Maven](http://maven.apache.org) 3 or later.
 
+{% include note.html content="While Java 9 is required for building, running PMD only requires Java 7 (or Java 8 for Apex)." %}
+
 You’ll need to either check out the source code or download the latest source release. Assuming you’ve got the latest source release, unzip it to a directory:
 
 ```
 [tom@hal building]$ ls -l
 total 5716
--rw-rw-r--    1 tom      tom       5837216 Jul 17 13:09 pmd-src-5.5.0.zip
-[tom@hal building]$ unzip -q pmd-src-5.5.0.zip
+-rw-rw-r--    1 tom      tom       5837216 Jul 17 13:09 pmd-src-{{site.pmd.version}}.zip
+[tom@hal building]$ unzip -q pmd-src-{{site.pmd.version}}.zip
 [tom@hal building]$
 ```
 
 Now cd down into the `pmd` directory:
 
 ```
-[tom@hal building]$ cd pmd-src-5.5.0
-[tom@hal pmd-src-5.5.0]$ ls -l | grep pom.xml
+[tom@hal building]$ cd pmd-src-{{site.pmd.version}}
+[tom@hal pmd-src-{{site.pmd.version}}]$ ls -l | grep pom.xml
 -rw-rw-r--    1 tom      tom          36482 14\. Nov 17:36 pom.xml
-[tom@hal pmd-src-5.5.0]$
+[tom@hal pmd-src-{{site.pmd.version}}]$
 ```
 
 That’s the project configuration for maven… let’s compile!
 
 ```
-[tom@hal pmd-src-5.5.0]$ mvn clean package
+[tom@hal pmd-src-{{site.pmd.version}}]$ ./mvnw clean verify
 [INFO] Scanning for projects...
 [INFO] ------------------------------------------------------------------------
 [INFO] Reactor Build Order:
@@ -71,13 +73,16 @@ That’s the project configuration for maven… let’s compile!
 [INFO] Finished at: 2015-11-14T17:46:06+01:00
 [INFO] Final Memory: 63M/765M
 [INFO] ------------------------------------------------------------------------
-[tom@hal pmd-src-5.5.0]$
+[tom@hal pmd-src-{{site.pmd.version}}]$
 ```
 
-Now the source and binary distribution zip files can be found in the folder <tt>pmd-dist/target</tt>.
+Now the source and binary distribution zip files can be found in the folder `pmd-dist/target`.
 
-Notes:
+**Notes:**
 
-*   The rules that have already been written are specified in the src/main/resources/rulesets/ directories of the specific languages, e.g. `pmd-java/src/main/resources/rulesets`. They’re also in the jar file that’s included with both the source and binary distributions.
+*   The rules that have already been written are specified in the `src/main/resources/rulesets/` directories of
+the specific languages, e.g. `pmd-java/src/main/resources/rulesets`.
+They’re also in the jar file that’s included with both the source and binary distributions.
 
-A paucity of detail, I’m sure you’d agree. If you think this document can be improved, please post [here](http://sourceforge.net/p/pmd/discussion/188192) and let me know how. Thanks!
+A paucity of detail, I’m sure you’d agree. If you think this document can be improved,
+please post [here](http://sourceforge.net/p/pmd/discussion/188192) and let me know how. Thanks!