i think it works now

.github/workflows/build.yml

@@ -59,4 +59,5 @@ jobs:
     - uses: pmd/pmd-github-action@v2
       with:
         rulesets: 'pmd-ruleset.xml'
-        analyzeModifiedFilesOnly: false
+        analyzeModifiedFilesOnly: false
+        # failOnWarnings: false

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+    "java.configuration.updateBuildConfiguration": "interactive"
+}

build.gradle

@@ -4,6 +4,7 @@ plugins {
     id "com.peterabeles.gversion" version "1.10"
     id "com.diffplug.spotless" version "6.25.0"
     id "com.google.protobuf" version "0.9.4"
+    id "pmd"
 }
 
 def grpcVersion = '1.61.0' // CURRENT_GRPC_VERSION
@@ -235,8 +236,8 @@ gversion {
     indent       = "  "
 }
 // Spotless formatting
-project.compileJava.dependsOn(spotlessApply)
 spotless {
+    enforceCheck = false
     java {
         target fileTree('.') {
             include '**/*.java'
@@ -279,13 +280,13 @@ spotless {
     }
 }
 
-// apply plugin: "pmd"
-
-// pmd {
-//     toolVersion = "7.3.0"
-//     consoleOutput = true
-//     sourceSets = [project.sourceSets["main"]]
-//     reportsDir = file("${project.buildDir}/reports/pmd")
-//     ruleSetFiles = files(file("$rootDir/pmd-ruleset.xml"))
-//     ruleSets = []
-// }
+// PMD configuration
+pmd {
+    ignoreFailures = true
+    toolVersion = "7.3.0"
+    consoleOutput = true
+    sourceSets = [project.sourceSets["main"]]
+    reportsDir = file("${project.buildDir}/reports/pmd")
+    ruleSetFiles = files(file("$rootDir/pmd-ruleset.xml"))
+    ruleSets = []
+}

pmd-ruleset.xml

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <ruleset name="WPILibRuleset"
-         xmlns="http://pmd.sourceforge.net/ruleset/2.0.0"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 http://pmd.sourceforge.net/ruleset_2_0_0.xsd">
+  xmlns="http://pmd.sourceforge.net/ruleset/2.0.0"
+  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 http://pmd.sourceforge.net/ruleset_2_0_0.xsd">
 
   <description>PMD Ruleset for WPILib</description>
 
@@ -34,7 +34,7 @@
   <rule ref="category/java/bestpractices.xml/UnusedPrivateMethod">
     <properties>
       <property name="violationSuppressRegex"
-                value=".*'.*Arguments\(\)'.*" />
+        value=".*'.*Arguments\(\)'.*" />
     </properties>
   </rule>
 

src/main/java/frc/robot/extras/regression/PolynomialRegression.java

@@ -174,6 +174,7 @@ public String toString() {
   }
 
   /** Compare lexicographically. */
+  @Override
   public int compareTo(PolynomialRegression that) {
     double EPSILON = 1E-5;
     int maxDegree = Math.max(this.degree(), that.degree());