Add checkstyle

checkstyle.xml

@@ -0,0 +1,100 @@
+<?xml version="1.0"?>
+<!--
+~    Copyright Skodjob Authors.
+~
+~    Licensed under the Apache Software License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+-->
+<!DOCTYPE module PUBLIC
+        "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
+        "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
+
+<module name="Checker">
+
+    <!-- Checks for whitespace                               -->
+    <!-- See http://checkstyle.sf.net/config_whitespace.html -->
+    <module name="FileTabCharacter"/>
+
+    <module name="LineLength">
+        <property name="max" value="120"/>
+    </module>
+
+    <module name="Header">
+        <property name="header"
+                  value="/*\n * Copyright Skodjob authors.\n * License: Apache License 2.0 (see the file LICENSE or http://apache.org/licenses/LICENSE-2.0.html).\n */"/>
+        <property name="fileExtensions" value="java"/>
+    </module>
+
+    <module name="TreeWalker">
+        <!-- Checks for Javadoc comments.                     -->
+        <!-- See http://checkstyle.sf.net/config_javadoc.html -->
+        <module name="MissingJavadocMethodCheck">
+            <property name="scope" value="public"/>
+            <property name="allowMissingPropertyJavadoc" value="true"/>
+            <property name="severity" value="warning" />
+        </module>
+        <module name="JavadocType">
+            <property name="scope" value="public"/>
+            <property name="severity" value="warning" />
+        </module>
+        <module name="JavadocStyle">
+            <property name="scope" value="public"/>
+            <property name="checkFirstSentence" value="false"/>
+            <property name="severity" value="warning" />
+        </module>
+
+        <!-- Checks for Naming Conventions.                  -->
+        <!-- See http://checkstyle.sf.net/config_naming.html -->
+        <module name="ConstantName"/>
+        <module name="LocalFinalVariableName"/>
+        <module name="LocalVariableName"/>
+        <module name="MemberName"/>
+        <module name="MethodName"/>
+        <module name="PackageName"/>
+        <module name="ParameterName"/>
+        <module name="StaticVariableName"/>
+        <module name="TypeName"/>
+
+        <!-- Checks for imports                              -->
+        <!-- See http://checkstyle.sf.net/config_import.html -->
+        <module name="AvoidStarImport">
+            <property name="severity" value="warning" />
+        </module>
+        <module name="IllegalImport"/> <!-- defaults to sun.* packages -->
+        <module name="RedundantImport"/>
+        <module name="UnusedImports"/>
+
+        <!-- Checks for Size Violations.                    -->
+        <!-- See http://checkstyle.sf.net/config_sizes.html -->
+
+        <module name="ParameterNumber"/>
+
+        <!-- Modifier Checks                                    -->
+        <!-- See http://checkstyle.sf.net/config_modifier.html -->
+        <module name="ModifierOrder"/>
+        <module name="RedundantModifier"/>
+
+        <!-- Checks for blocks. You know, those {}'s         -->
+        <!-- See http://checkstyle.sf.net/config_blocks.html -->
+        <module name="AvoidNestedBlocks"/>
+        <module name="LeftCurly">
+            <property name="option" value="eol"/>
+        </module>
+        <module name="NeedBraces">
+            <property name="allowSingleLineStatement" value="true"/>
+        </module>
+        <module name="RightCurly"/>
+
+        <!-- Checks for common coding problems               -->
+        <!-- See http://checkstyle.sf.net/config_coding.html -->
+        <module name="EmptyStatement"/>
+        <module name="EqualsHashCode"/>
+        <module name="MissingSwitchDefault"/>
+        <module name="SimplifyBooleanExpression"/>
+        <module name="SimplifyBooleanReturn"/>
+
+        <!-- Miscellaneous other checks.                   -->
+        <!-- See http://checkstyle.sf.net/config_misc.html -->
+        <module name="ArrayTypeStyle"/>
+
+    </module>
+</module>

pom.xml

@@ -82,6 +82,7 @@
         <maven.javadoc.version>3.4.1</maven.javadoc.version>
         <maven.assembly.version>3.4.2</maven.assembly.version>
         <maven.plugin.plugin.version>3.9.0</maven.plugin.plugin.version>
+        <checkstyle.config.location>checkstyle.xml</checkstyle.config.location>
         <junit.jupiter.version>5.10.2</junit.jupiter.version>
     </properties>
 
@@ -250,6 +251,24 @@
                             </execution>
                         </executions>
                     </plugin>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-checkstyle-plugin</artifactId>
+                        <version>${maven.checkstyle.version}</version>
+                        <executions>
+                            <execution>
+                                <id>validate</id>
+                                <phase>validate</phase>
+                                <configuration>
+                                    <consoleOutput>true</consoleOutput>
+                                    <failsOnError>true</failsOnError>
+                                </configuration>
+                                <goals>
+                                    <goal>check</goal>
+                                </goals>
+                            </execution>
+                        </executions>
+                    </plugin>
                 </plugins>
             </build>
         </profile>