add checkstyle

Signed-off-by: Gregor Zeitlinger <[email protected]>

Author: zeitlinger

checkstyle.xml

@@ -371,15 +371,6 @@
     <module name="SuppressWarningsHolder"/>
     <!-- this enables CHECKSTYLE:OFF and CHECKSTYLE:ON comments -->
     <module name="SuppressionCommentFilter"/>
-    <module name="Regexp">
-      <!-- see comment in otel.errorprone-conventions.gradle.kts for why we disable the SystemOut
-           rule there and rely on this check -->
-      <property name="id" value="SystemOut"/>
-      <!-- . matches any character, so we need to escape it and use \. to match dots. -->
-      <property name="format"
-        value="(System\.out\.print|System\.err\.print|\.printStackTrace\(\)|Thread\.dumpStack)"/>
-      <property name="illegalPattern" value="true"/>
-    </module>
   </module>
   <!-- this enables @SuppressWarnings("checkstyle:...") annotations -->
   <module name="SuppressWarningsFilter"/>

integration-tests/it-exporter/it-exporter-servlet-jetty-sample/src/main/java/io/prometheus/metrics/it/exporter/servlet/jetty/ExporterServletJettySample.java

@@ -29,7 +29,10 @@ public static void main(String[] args) throws Exception {
 
     int port = parsePortOrExit(args[0]);
     Mode mode = parseModeOrExit(args[1]);
+    run(mode, port);
+  }
 
+  private static void run(Mode mode, int port) throws Exception {
     Counter counter =
         Counter.builder()
             .name("uptime_seconds_total")

integration-tests/it-exporter/it-exporter-servlet-tomcat-sample/src/main/java/io/prometheus/metrics/it/exporter/servlet/tomcat/ExporterServletTomcatSample.java

@@ -30,11 +30,12 @@ public static void main(String[] args) throws LifecycleException, IOException {
       System.exit(1);
     }
 
-    //noinspection CheckStyle
     int port = parsePortOrExit(args[0]);
-    //noinspection CheckStyle
     Mode mode = parseModeOrExit(args[1]);
+    run(mode, port);
+  }
 
+  private static void run(Mode mode, int port) throws IOException, LifecycleException {
     Counter counter =
         Counter.builder()
             .name("uptime_seconds_total")