Add COMPILING.md and set Java Version to 16

COMPILING.md

@@ -0,0 +1,42 @@
+Compiling
+=========
+
+You can compile WorldGuard as long as you have some version of Java greater than or equal to 16 installed. Gradle will download JDK 16 specifically if needed,
+but it needs some version of Java to bootstrap from.
+
+Note that if you have JRE 16 installed, Gradle will currently attempt to use that to compile, which will not work. It is easiest to uninstall JRE 16 and
+replace it with JDK 16.
+
+The build process uses Gradle, which you do *not* need to download. WorldGuard is a multi-module project with four modules:
+
+* `worldguard-core` contains the WorldGuard API
+* `worldguard-bukkit` is the Bukkit plugin
+* `worldguard-libs` contains library relocations
+
+## To compile...
+
+### On Windows
+
+1. Shift + right click the folder with WorldGuard's files and click "Open command prompt".
+2. `gradlew build`
+
+### On Linux, BSD, or Mac OS X
+
+1. In your terminal, navigate to the folder with WorldGuard's files (`cd /folder/of/worldguard/files`)
+2. `./gradlew build`
+
+## Then you will find...
+
+You will find:
+
+* The core WorldGuard API in **worldguard-core/build/libs**
+* WorldGuard for Bukkit in **worldguard-bukkit/build/libs**
+
+If you want to use WorldGuard, use the `-dist` version.
+
+(The -dist version includes WorldGuard + necessary libraries.)
+
+## Other commands
+
+* `gradlew idea` will generate an [IntelliJ IDEA](http://www.jetbrains.com/idea/) module for each folder.
+* `gradlew eclipse` will generate an [Eclipse](https://www.eclipse.org/downloads/) project for each folder.

CONTRIBUTING.md

@@ -7,7 +7,7 @@ ask that you make note of the following guidelines.
 * **Follow the [Oracle coding conventions](https://www.oracle.com/technetwork/java/javase/documentation/codeconvtoc-136057.html).**
   We can't stress this enough; if your code has notable issues, it may delay
   the process significantly.
-* **Target Java 8 for source and compilation.** Make sure to mark methods with
+* **Target Java 16 for source and compilation.** Make sure to mark methods with
   ` @Override` that override methods of parent classes, or that implement
   methods of interfaces.
 * **Use only spaces for indentation.** Our indents are 4-spaces long, and tabs

README.md

@@ -23,7 +23,7 @@ A Bukkit server implementation (such as [Paper](https://papermc.io)) and the [Wo
 Compiling
 ---------
 
-The project is written for Java 17 and our build process makes use of
+The project is written for Java 16 and our build process makes use of
 [Gradle](http://gradle.org).
 
 Dependencies are automatically handled by Gradle.