Add and apply Checkstyle config.

build.gradle

@@ -55,6 +55,7 @@ subprojects {
   apply plugin: 'signing'
   apply plugin: 'maven'
   apply plugin: 'jacoco'
+  apply plugin: 'checkstyle'
 
   check.dependsOn(editorconfigCheck)
 
@@ -85,6 +86,11 @@ subprojects {
     archives javadocJar
   }
 
+  checkstyle {
+    toolVersion '8.30'
+    checkstyleTest.enabled = false
+  }
+
   signing {
     required {
       scmInfo.isRelease() && gradle.taskGraph.hasTask(tasks.uploadArchives)

config/checkstyle/checkstyle.xml

@@ -0,0 +1,167 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE module PUBLIC
+    "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+    "https://checkstyle.org/dtds/configuration_1_3.dtd">
+<module name="Checker">
+    <module name="SuppressWarningsFilter" />
+    <module name="SuppressionSingleFilter">
+        <property name="checks" value=".*"/>
+        <property name="files" value="generated-src"/>
+    </module>
+    <module name="TreeWalker">
+        <module name="AbstractClassName"/>
+        <module name="AnnotationUseStyle"/>
+        <module name="AnonInnerLength"/>
+        <module name="ArrayTypeStyle"/>
+        <module name="AvoidNestedBlocks"/>
+        <module name="AvoidNoArgumentSuperConstructorCall"/>
+        <module name="AvoidStarImport"/>
+        <module name="AvoidStaticImport"/>
+        <module name="BooleanExpressionComplexity"/>
+        <module name="CatchParameterName">
+            <property name="format" value="^e$"/>
+        </module>
+        <module name="ClassDataAbstractionCoupling"/>
+        <module name="ClassFanOutComplexity"/>
+        <module name="ClassTypeParameterName"/>
+        <module name="ConstantName"/>
+        <module name="CovariantEquals"/>
+        <module name="CustomImportOrder">
+            <property name="customImportOrderRules" value="SAME_PACKAGE(2)###THIRD_PARTY_PACKAGE###STANDARD_JAVA_PACKAGE###SPECIAL_IMPORTS###STATIC"/>
+            <property name="separateLineBetweenGroups" value="true"/>
+        </module>
+        <module name="CyclomaticComplexity"/>
+        <module name="DeclarationOrder"/>
+        <module name="DefaultComesLast"/>
+        <module name="EmptyLineSeparator">
+            <property name="allowMultipleEmptyLines" value="false"/>
+            <property name="allowMultipleEmptyLinesInsideClassMembers" value="false"/>
+            <property name="allowNoEmptyLineBetweenFields" value="true"/>
+        </module>
+        <module name="EmptyStatement"/>
+        <module name="EqualsAvoidNull"/>
+        <module name="EqualsHashCode"/>
+        <module name="ExecutableStatementCount"/>
+        <module name="ExplicitInitialization"/>
+        <module name="FallThrough"/>
+        <module name="FinalLocalVariable">
+            <property name="validateEnhancedForLoopVariable" value="true"/>
+        </module>
+        <module name="FinalParameters">
+            <property name="tokens" value="CTOR_DEF,LITERAL_CATCH,METHOD_DEF"/>
+        </module>
+        <module name="GenericWhitespace"/>
+        <module name="HiddenField">
+            <property name="ignoreConstructorParameter" value="true"/>
+            <property name="ignoreSetter" value="true"/>
+        </module>
+        <module name="HideUtilityClassConstructor"/>
+        <module name="IllegalCatch"/>
+        <module name="IllegalThrows"/>
+        <module name="IllegalToken">
+            <property name="tokens" value="POST_INC,POST_DEC"/>
+        </module>
+        <module name="IllegalType"/>
+        <module name="Indentation"/>
+        <module name="InnerAssignment"/>
+        <module name="InnerTypeLast"/>
+        <module name="InterfaceIsType"/>
+        <module name="InterfaceTypeParameterName"/>
+        <module name="JavaNCSS"/>
+        <module name="JavadocType"/>
+        <module name="LambdaParameterName"/>
+        <module name="LeftCurly"/>
+        <module name="LocalFinalVariableName"/>
+        <module name="LocalVariableName"/>
+        <module name="MagicNumber"/>
+        <module name="MemberName"/>
+        <module name="MethodLength"/>
+        <module name="MethodName"/>
+        <module name="MethodParamPad"/>
+        <module name="MethodTypeParameterName"/>
+        <module name="MissingCtor"/>
+        <module name="MissingDeprecated"/>
+        <module name="MissingOverride"/>
+        <module name="MissingSwitchDefault"/>
+        <module name="ModifiedControlVariable"/>
+        <module name="ModifierOrder"/>
+        <module name="MultipleStringLiterals">
+            <property name="allowedDuplicates" value="2"/>
+            <property name="ignoreStringsRegexp" value="^&quot;.?.?&quot;$"/>
+        </module>
+        <module name="MultipleVariableDeclarations"/>
+        <module name="MutableException"/>
+        <module name="NeedBraces"/>
+        <module name="NPathComplexity"/>
+        <module name="NoArrayTrailingComma"/>
+        <module name="NoClone"/>
+        <module name="NoEnumTrailingComma"/>
+        <module name="NoFinalizer"/>
+        <module name="NoWhitespaceAfter"/>
+        <module name="NoWhitespaceBefore"/>
+        <module name="OneStatementPerLine">
+            <property name="treatTryResourcesAsStatement" value="true"/>
+        </module>
+        <module name="OneTopLevelClass"/>
+        <module name="OperatorWrap">
+            <property name="option" value="eol"/>
+        </module>
+        <module name="OuterTypeFilename"/>
+        <module name="OuterTypeNumber"/>
+        <module name="OverloadMethodsDeclarationOrder"/>
+        <module name="PackageDeclaration"/>
+        <module name="PackageName"/>
+        <module name="ParameterAssignment"/>
+        <module name="ParameterName"/>
+        <module name="ParameterNumber">
+            <property name="max" value="5"/>
+        </module>
+        <module name="ParenPad"/>
+        <module name="RedundantImport"/>
+        <module name="RedundantModifier"/>
+        <module name="RequireThis"/>
+        <module name="ReturnCount"/>
+        <module name="RightCurly">
+            <property name="option" value="alone"/>
+        </module>
+        <module name="SeparatorWrap">
+            <property name="tokens" value="COMMA,SEMI,ELLIPSIS,ARRAY_DECLARATOR"/>
+            <property name="option" value="eol"/>
+        </module>
+        <module name="SeparatorWrap">
+            <property name="tokens" value="DOT,AT,METHOD_REF"/>
+            <property name="option" value="nl"/>
+        </module>
+        <module name="SimplifyBooleanExpression"/>
+        <module name="SimplifyBooleanReturn"/>
+        <module name="StaticVariableName"/>
+        <module name="StringLiteralEquality"/>
+        <module name="SuperClone"/>
+        <module name="SuperFinalize"/>
+        <module name="SuppressWarnings">
+            <!-- allow: fallthrough, unchecked (cf. https://docs.oracle.com/javase/8/docs/technotes/tools/unix/javac.html#BHCJBHDF) -->
+            <property name="format" value="^\s*(?:all|cast|classfile|deprecation|dep-ann|divzero|empty|finally|options|overrides|path|processing|rawtypes|Serial|static|try|varargs)\s*$"/>
+        </module>
+        <module name="SuppressWithNearbyCommentFilter">
+            <property name="checkFormat" value="$1"/>
+            <property name="commentFormat" value="checkstyle-disable-line (\w+(?:\|\w+)?)"/>
+        </module>
+        <module name="SuppressWarningsHolder" />
+        <module name="ThrowsCount">
+            <property name="max" value="2"/>
+        </module>
+        <module name="TypecastParenPad"/>
+        <module name="TypeName"/>
+        <module name="UnnecessaryParentheses"/>
+        <module name="UnnecessarySemicolonAfterTypeMemberDeclaration"/>
+        <module name="UnnecessarySemicolonInEnumeration"/>
+        <module name="UnnecessarySemicolonInTryWithResources">
+            <property name="allowWhenNoBraceAfterSemicolon" value="false"/>
+        </module>
+        <module name="UnusedImports"/>
+        <module name="UpperEll"/>
+        <module name="VisibilityModifier"/>
+        <module name="WhitespaceAfter"/>
+        <module name="WhitespaceAround"/>
+    </module>
+</module>

metafacture-biblio/src/main/java/org/metafacture/biblio/AlephMabXmlHandler.java

@@ -12,6 +12,7 @@
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  */
+
 package org.metafacture.biblio;
 
 import org.metafacture.framework.FluxCommand;
@@ -21,6 +22,7 @@
 import org.metafacture.framework.annotations.In;
 import org.metafacture.framework.annotations.Out;
 import org.metafacture.framework.helpers.DefaultXmlPipe;
+
 import org.xml.sax.Attributes;
 import org.xml.sax.SAXException;
 
@@ -48,6 +50,9 @@ public final class AlephMabXmlHandler extends DefaultXmlPipe<StreamReceiver> {
     private String currentTag = "";
     private StringBuilder builder = new StringBuilder();
 
+    public AlephMabXmlHandler() {
+    }
+
     @Override
     public void characters(final char[] chars, final int start, final int length)
             throws SAXException {
@@ -60,11 +65,14 @@ public void endElement(final String uri, final String localName, final String qN
         if (AlephMabXmlHandler.CONTROLLFIELD.equals(localName)) {
             getReceiver().literal(this.currentTag, this.builder.toString().trim());
             getReceiver().endEntity();
-        } else if (AlephMabXmlHandler.SUBFIELD.equals(localName)) {
+        }
+        else if (AlephMabXmlHandler.SUBFIELD.equals(localName)) {
             getReceiver().literal(this.currentTag, this.builder.toString().trim());
-        } else if (AlephMabXmlHandler.DATAFIELD.equals(localName)) {
+        }
+        else if (AlephMabXmlHandler.DATAFIELD.equals(localName)) {
             getReceiver().endEntity();
-        } else if (AlephMabXmlHandler.RECORD.equals(localName)) {
+        }
+        else if (AlephMabXmlHandler.RECORD.equals(localName)) {
             getReceiver().endRecord();
         }
     }
@@ -76,16 +84,20 @@ public void startElement(final String uri, final String localName, final String
             this.builder = new StringBuilder();
             this.currentTag = "";
             getReceiver().startEntity(attributes.getValue(AlephMabXmlHandler.DATAFIELD_ATTRIBUTE));
-        } else if (AlephMabXmlHandler.SUBFIELD.equals(localName)) {
+        }
+        else if (AlephMabXmlHandler.SUBFIELD.equals(localName)) {
             this.builder = new StringBuilder();
             this.currentTag = attributes.getValue(AlephMabXmlHandler.SUBFIELD_ATTRIBUTE);
-        } else if (AlephMabXmlHandler.DATAFIELD.equals(localName)) {
-            getReceiver().startEntity(attributes.getValue(AlephMabXmlHandler.DATAFIELD_ATTRIBUTE)
-                    + attributes.getValue(AlephMabXmlHandler.INDICATOR1)
-                    + attributes.getValue(AlephMabXmlHandler.INDICATOR2));
-        } else if (AlephMabXmlHandler.RECORD.equals(localName)) {
+        }
+        else if (AlephMabXmlHandler.DATAFIELD.equals(localName)) {
+            getReceiver().startEntity(attributes.getValue(AlephMabXmlHandler.DATAFIELD_ATTRIBUTE) +
+                    attributes.getValue(AlephMabXmlHandler.INDICATOR1) +
+                    attributes.getValue(AlephMabXmlHandler.INDICATOR2));
+        }
+        else if (AlephMabXmlHandler.RECORD.equals(localName)) {
             getReceiver().startRecord("");
-        } else if (AlephMabXmlHandler.LEADER.equals(localName)) {
+        }
+        else if (AlephMabXmlHandler.LEADER.equals(localName)) {
             this.builder = new StringBuilder();
             this.currentTag = AlephMabXmlHandler.LEADER;
         }

metafacture-biblio/src/main/java/org/metafacture/biblio/AseqDecoder.java

@@ -13,6 +13,7 @@
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  */
+
 package org.metafacture.biblio;
 
 import org.metafacture.framework.FluxCommand;
@@ -31,11 +32,19 @@
 @In(String.class)
 @Out(StreamReceiver.class)
 @FluxCommand("decode-aseq")
-public final class AseqDecoder
-        extends DefaultObjectPipe<String, StreamReceiver> {
+public final class AseqDecoder extends DefaultObjectPipe<String, StreamReceiver> {
 
     private static final String FIELD_DELIMITER = "\n";
 
+    private static final int CATEGORY_BEGIN = 10;
+    private static final int CATEGORY_END = 15;
+    private static final int FIELD_CONTENT_BEGIN = 18;
+    private static final int RECORD_IDENTIFIER_BEGIN = 0;
+    private static final int RECORD_IDENTIFIER_END = 9;
+
+    public AseqDecoder() {
+    }
+
     @Override
     public void process(final String record) {
         assert !isClosed();
@@ -44,16 +53,17 @@ public void process(final String record) {
             return;
         }
         final String[] lines = trimedRecord.split(FIELD_DELIMITER);
-        for (int i = 0; i < lines.length; i++) {
+        for (int i = 0; i < lines.length; ++i) {
             final String field = lines[i];
             if (i == 0) {
-                getReceiver().startRecord(field.substring(0, 9));
+                getReceiver().startRecord(field.substring(RECORD_IDENTIFIER_BEGIN, RECORD_IDENTIFIER_END));
             }
-            final String category = field.substring(10, 15).trim();
-            final String fieldContent = field.substring(18).trim();
+            final String category = field.substring(CATEGORY_BEGIN, CATEGORY_END).trim();
+            final String fieldContent = field.substring(FIELD_CONTENT_BEGIN).trim();
             if (!fieldContent.startsWith("$$")) {
                 getReceiver().literal(category, fieldContent);
-            } else {
+            }
+            else {
                 getReceiver().startEntity(category);
                 final String[] subfields = fieldContent.split("\\$\\$");
                 for (final String subfield : subfields) {