diff --git a/etc/pmd-configuration.xml b/etc/pmd-configuration.xml
index 927db432..f3b054f1 100644
--- a/etc/pmd-configuration.xml
+++ b/etc/pmd-configuration.xml
@@ -3,7 +3,7 @@
 <ruleset xmlns="http://pmd.sourceforge.net/ruleset/2.0.0"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          name="pmd-eclipse"
-         xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 http://pmd.sourceforge.net/ruleset_2_0_0.xsd">
+         xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 https://pmd.sourceforge.io/ruleset_2_0_0.xsd">
   <description>Ullrich Hafner's PMD rules</description>
 
   <rule ref="category/java/bestpractices.xml">
@@ -16,6 +16,12 @@
     <exclude name="JUnit5TestShouldBePackagePrivate"/>
     <exclude name="JUnit4TestShouldUseTestAnnotation"/>
     <exclude name="UnusedPrivateMethod"/>
+    <exclude name="LooseCoupling"/>
+  </rule>
+  <rule ref="category/java/bestpractices.xml/LooseCoupling">
+    <properties>
+      <property name="allowedTypes" value="com.tngtech.archunit.core.domain.JavaClasses"/>
+    </properties>
   </rule>
   <rule ref="category/java/codestyle.xml">
     <exclude name="EmptyControlStatement"/>
@@ -67,6 +73,12 @@
     <exclude name="FinalFieldCouldBeStatic"/>
     <exclude name="AvoidUncheckedExceptionsInSignatures"/>
     <exclude name="ExcessiveImports"/>
+    <exclude name="SimplifyBooleanReturns"/>
+  </rule>
+  <rule ref="category/java/design.xml/SimplifyBooleanReturns">
+    <properties>
+      <property name="violationSuppressXPath" value="./ancestor::*[@Name = 'equals']"/>
+    </properties>
   </rule>
   <rule ref="category/java/errorprone.xml">
     <exclude name="AvoidDuplicateLiterals"/>
diff --git a/src/main/java/edu/hm/hafner/util/TreeString.java b/src/main/java/edu/hm/hafner/util/TreeString.java
index 775cd88e..6593c3ac 100644
--- a/src/main/java/edu/hm/hafner/util/TreeString.java
+++ b/src/main/java/edu/hm/hafner/util/TreeString.java
@@ -52,7 +52,7 @@ public final class TreeString implements Serializable {
     }
 
     String getLabel() {
-        return new String(label);
+        return String.valueOf(label);
     }
 
     /**
diff --git a/src/test/java/edu/hm/hafner/util/ArchitectureRules.java b/src/test/java/edu/hm/hafner/util/ArchitectureRules.java
index 6791e901..f4c5936f 100644
--- a/src/test/java/edu/hm/hafner/util/ArchitectureRules.java
+++ b/src/test/java/edu/hm/hafner/util/ArchitectureRules.java
@@ -30,6 +30,7 @@
  *
  * @author Ullrich Hafner
  */
+@SuppressWarnings("PMD.DataClass")
 public final class ArchitectureRules {
     /** Tests should not use fields. Recommendation is to use factory methods for stubs and mocks. */
     public static final ArchRule NO_FIELDS_IN_TESTS =
diff --git a/src/test/java/edu/hm/hafner/util/LineRangeListTest.java b/src/test/java/edu/hm/hafner/util/LineRangeListTest.java
index 3f1d0e97..318efe8d 100644
--- a/src/test/java/edu/hm/hafner/util/LineRangeListTest.java
+++ b/src/test/java/edu/hm/hafner/util/LineRangeListTest.java
@@ -1,5 +1,7 @@
 package edu.hm.hafner.util;
 
+import java.util.List;
+
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.*;
@@ -75,15 +77,15 @@ void shouldResizeCorrectly() {
 
     @Test
     void shouldProvideContains() {
-        LineRangeList last = createThreeElements();
+        var last = createThreeElements();
         last.remove(new LineRange(4, 5));
         assertThat(last).containsExactly(new LineRange(0, 1), new LineRange(2, 3));
 
-        LineRangeList middle = createThreeElements();
+        var middle = createThreeElements();
         middle.remove(new LineRange(2, 3));
         assertThat(middle).containsExactly(new LineRange(0, 1), new LineRange(4, 5));
 
-        LineRangeList first = createThreeElements();
+        var first = createThreeElements();
         assertThat(first.contains(new LineRange(0, 1))).isTrue();
         assertThat(first.contains(new LineRange(2, 3))).isTrue();
         assertThat(first.contains(new LineRange(4, 5))).isTrue();
@@ -95,7 +97,7 @@ void shouldProvideContains() {
         assertThat(first.contains(new LineRange(0, 1))).isFalse();
     }
 
-    private LineRangeList createThreeElements() {
+    private List<LineRange> createThreeElements() {
         var range = new LineRangeList();
         range.add(new LineRange(0, 1));
         range.add(new LineRange(2, 3));