Added checkstyle.

- Added maven's checkstyle plugin (applies to main and test .java files).
- Added a check for line length <= 120 (currently marked as ignored due to >7000 violations).
- Disallow whitespace indents (force TABs).
- Disallow star imports (import blabla.*).
- Disallow empty blocks ({}).
- Disallow trailing whitespaces/tabs.

Author: Pieter12345

checkstyle.xml

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE module PUBLIC "-//Puppy Crawl//DTD Check Configuration 1.3//EN" "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
+
+<!--
+    Checkstyle-Configuration: CommandHelper
+    Description: A checkstyle configuration for CommandHelper.
+    Author: P.J.S. Kools
+-->
+<module name="Checker">
+    <property name="severity" value="error"/>
+    <module name="TreeWalker">
+        
+        <!-- Line length <= 120 characters. -->
+        <module name="LineLength">
+            <property name="severity" value="ignore"/> <!-- TODO: Change to "error" once the >7000 violations have been resolved. -->
+            <property name="max" value="120"/>
+        </module>
+        
+        <!-- Indent must use tab characters. -->
+        <module name="RegexpSinglelineJava">
+            <property name="format" value="^\t* ([^\*]|$)"/> <!-- Javadoc and multiline comments have a single leading whitespace, so allow " *". -->
+            <property name="message" value="Indent must use tab characters"/>
+            <property name="ignoreComments" value="false"/>
+        </module>
+        
+        <module name="AvoidStarImport"/>
+        <module name="EmptyBlock"/>
+        
+    </module>
+    
+    <!-- Disallow trailing whitespaces/tabs. -->
+    <module name="RegexpSingleline">
+        <property name="severity" value="error"/>
+        <property name="format" value="(?&lt;! \*)\s+$"/> <!-- Empty javadoc and multiline comment lines have a single trailing whitespace, so allow " * ". -->
+        <property name="message" value="Line has trailing whitespaces/tabs."/>
+        <metadata name="net.sf.eclipsecs.core.lastEnabledSeverity" value="inherit"/>
+    </module>
+</module>

pom.xml

@@ -200,10 +200,10 @@
 		<!-- Used for IRC hooks -->
 		<!-- NOT READY YET
 		<dependency>
-			 <groupId>org.jibble</groupId>
-			 <artifactId>pircbot</artifactId>
-			 <version>1.5.0</version>
-			 <scope>compile</scope>
+			<groupId>org.jibble</groupId>
+			<artifactId>pircbot</artifactId>
+			<version>1.5.0</version>
+			<scope>compile</scope>
 		</dependency>
 		-->
 
@@ -280,17 +280,17 @@
 
 		<!-- Evil-y things (currently not used) -->
 		<!--<dependency>
-		 <groupId>cglib</groupId>
-		 <artifactId>cglib</artifactId>
-		 <version>2.2.2</version>
-		 <scope>compile</scope>
-		 <type>jar</type>
+		<groupId>cglib</groupId>
+		<artifactId>cglib</artifactId>
+		<version>2.2.2</version>
+		<scope>compile</scope>
+		<type>jar</type>
 		</dependency>
 		<dependency>
-		 <groupId>org.javassist</groupId>
-		 <artifactId>javassist</artifactId>
-		 <version>3.15.0-GA</version>
-		 <type>jar</type>
+		<groupId>org.javassist</groupId>
+		<artifactId>javassist</artifactId>
+		<version>3.15.0-GA</version>
+		<type>jar</type>
 		</dependency>-->
 		<!-- Embedded SSH Client -->
 		<dependency>
@@ -914,6 +914,33 @@
 					</execution>
 				</executions>
 			</plugin>
+			
+			<!-- Checkstyle plugin -->
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-checkstyle-plugin</artifactId>
+				<version>3.0.0</version>
+				<executions>
+					<execution>
+						<id>validate</id>
+						<phase>validate</phase>
+						<configuration>
+							<sourceDirectories>${project.compileSourceRoots}</sourceDirectories>
+							<testSourceDirectories>${project.testCompileSourceRoots}</testSourceDirectories>
+							<includeTestSourceDirectory>true</includeTestSourceDirectory>
+							<configLocation>${basedir}/checkstyle.xml</configLocation>
+							<encoding>UTF-8</encoding>
+							<consoleOutput>true</consoleOutput>
+							<failsOnError>true</failsOnError>
+							<linkXRef>false</linkXRef>
+						</configuration>
+						<goals>
+							<goal>check</goal>
+						</goals>
+					</execution>
+				</executions>
+			</plugin>
+			
 		</plugins>
 	</build>
 	<profiles>