Enable PrivateConstructorForUtilityClass errorprone check (#6427)

* PrivateConstructorForUtilityClass

* Advice

* More advice

* More

* More advice

* More

* Spotless

* Fix

* Fix

* Fix

* A better solution

* Revert

* More

* Fix

* Spotless

* Fix

conventions/src/main/kotlin/otel.errorprone-conventions.gradle.kts

@@ -89,9 +89,8 @@ tasks {
         // allow UPPERCASE type parameter names
         disable("TypeParameterNaming")
 
-        // Great check, but for bytecode manipulation it's too common to separate over
+        // In bytecode instrumentation it's very common to separate across onEnter / onExit
-        // onEnter / onExit
+        // TODO(anuraaga): Only disable for javaagent instrumentation modules.
-        // TODO(anuraaga): Only disable for auto instrumentation project.
         disable("MustBeClosedChecker")
 
         // Common to avoid an allocation. Revisit if it's worth opt-in suppressing instead of
@@ -106,8 +105,7 @@ tasks {
         // some moving.
         disable("DefaultPackage")
 
-        // TODO(anuraaga): Remove this, all our advice classes miss constructors but probably should
+        // we use modified OtelPrivateConstructorForUtilityClass which ignores *Advice classes
-        // address this.
         disable("PrivateConstructorForUtilityClass")
 
         // TODO(anuraaga): Remove this, probably after instrumenter API migration instead of dealing

custom-checks/src/main/java/io/opentelemetry/javaagent/customchecks/OtelPrivateConstructorForUtilityClass.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.customchecks;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.matchers.Description.NO_MATCH;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.PrivateConstructorForUtilityClass;
+import com.google.errorprone.matchers.Description;
+import com.sun.source.tree.ClassTree;
+
+@AutoService(BugChecker.class)
+@BugPattern(
+    summary =
+        "Classes which are not intended to be instantiated should be made non-instantiable with a private constructor. This includes utility classes (classes with only static members), and the main class.",
+    severity = WARNING)
+public class OtelPrivateConstructorForUtilityClass extends BugChecker
+    implements BugChecker.ClassTreeMatcher {
+
+  private static final long serialVersionUID = 1L;
+
+  private final PrivateConstructorForUtilityClass delegate =
+      new PrivateConstructorForUtilityClass();
+
+  @Override
+  public Description matchClass(ClassTree tree, VisitorState state) {
+    if (tree.getSimpleName().toString().endsWith("Advice")) {
+      return NO_MATCH;
+    }
+    Description description = delegate.matchClass(tree, state);
+    if (description == NO_MATCH) {
+      return description;
+    }
+    return describeMatch(tree);
+  }
+}

instrumentation-annotations-support/src/test/java/io/opentelemetry/instrumentation/api/annotation/support/MethodCacheTest.java

@@ -83,6 +83,9 @@ public class MethodCacheTest {
   }
 
   static class TestClass {
+
     public static void method() {}
+
+    private TestClass() {}
   }
 }

instrumentation-api-semconv/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/rpc/MetricsView.java

@@ -112,4 +112,6 @@ final class MetricsView {
               }
             });
   }
+
+  private MetricsView() {}
 }

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/LocalRootSpan.java

@@ -54,4 +54,6 @@ public final class LocalRootSpan {
   static Context store(Context context, Span span) {
     return context.with(KEY, span);
   }
+
+  private LocalRootSpan() {}
 }

instrumentation/akka/akka-http-10.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/akkahttp/client/FutureWrapper.java

@@ -13,7 +13,8 @@ import scala.concurrent.impl.Promise;
 import scala.runtime.AbstractFunction1;
 import scala.util.Try;
 
-public class FutureWrapper {
+public final class FutureWrapper {
+
   public static <T> Future<T> wrap(
       Future<T> future, ExecutionContext executionContext, Context context) {
     Promise.DefaultPromise<T> promise = new Promise.DefaultPromise<>();
@@ -31,4 +32,6 @@ public class FutureWrapper {
 
     return promise;
   }
+
+  private FutureWrapper() {}
 }

instrumentation/akka/akka-http-10.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/akkahttp/server/AkkaHttpServerSingletons.java

@@ -17,7 +17,7 @@ import io.opentelemetry.instrumentation.api.instrumenter.http.HttpSpanStatusExtr
 import io.opentelemetry.javaagent.bootstrap.internal.CommonConfig;
 import io.opentelemetry.javaagent.instrumentation.akkahttp.AkkaHttpUtil;
 
-public class AkkaHttpServerSingletons {
+public final class AkkaHttpServerSingletons {
 
   private static final Instrumenter<HttpRequest, HttpResponse> INSTRUMENTER;
 
@@ -46,4 +46,6 @@ public class AkkaHttpServerSingletons {
   public static HttpResponse errorResponse() {
     return (HttpResponse) HttpResponse.create().withStatus(500);
   }
+
+  private AkkaHttpServerSingletons() {}
 }

instrumentation/apache-httpclient/apache-httpclient-4.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/apachehttpclient/v4_0/ApacheHttpClientHelper.java

@@ -22,4 +22,6 @@ public final class ApacheHttpClientHelper {
       // ended in WrappingStatusSettingResponseHandler
     }
   }
+
+  private ApacheHttpClientHelper() {}
 }

instrumentation/apache-httpclient/apache-httpclient-5.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/apachehttpclient/v5_0/ApacheHttpClientHelper.java

@@ -23,4 +23,6 @@ public class ApacheHttpClientHelper {
       // ended in WrappingStatusSettingResponseHandler
     }
   }
+
+  private ApacheHttpClientHelper() {}
 }

instrumentation/armeria-1.3/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/armeria/v1_3/AbstractStreamMessageSubscriptionInstrumentation.java

@@ -51,6 +51,7 @@ public class AbstractStreamMessageSubscriptionInstrumentation implements TypeIns
     }
   }
 
+  @SuppressWarnings("unused")
   public static class WrapCompletableFutureAdvice {
 
     @Advice.OnMethodEnter(suppress = Throwable.class)

instrumentation/aws-lambda/aws-lambda-core-1.0/library/src/main/java/io/opentelemetry/instrumentation/awslambdacore/v1_0/internal/AwsLambdaFunctionInstrumenterFactory.java

@@ -14,7 +14,7 @@ import io.opentelemetry.instrumentation.awslambdacore.v1_0.AwsLambdaRequest;
  * This class is internal and is hence not for public use. Its APIs are unstable and can change at
  * any time.
  */
-public class AwsLambdaFunctionInstrumenterFactory {
+public final class AwsLambdaFunctionInstrumenterFactory {
 
   public static AwsLambdaFunctionInstrumenter createInstrumenter(OpenTelemetry openTelemetry) {
     return new AwsLambdaFunctionInstrumenter(
@@ -30,4 +30,6 @@ public class AwsLambdaFunctionInstrumenterFactory {
   private static String spanName(AwsLambdaRequest input) {
     return input.getAwsContext().getFunctionName();
   }
+
+  private AwsLambdaFunctionInstrumenterFactory() {}
 }

instrumentation/aws-lambda/aws-lambda-events-2.2/library/src/main/java/io/opentelemetry/instrumentation/awslambdaevents/v2_2/internal/AwsLambdaEventsInstrumenterFactory.java

@@ -17,7 +17,7 @@ import io.opentelemetry.instrumentation.awslambdacore.v1_0.internal.AwsLambdaFun
  * This class is internal and is hence not for public use. Its APIs are unstable and can change at
  * any time.
  */
-public class AwsLambdaEventsInstrumenterFactory {
+public final class AwsLambdaEventsInstrumenterFactory {
 
   public static AwsLambdaFunctionInstrumenter createInstrumenter(OpenTelemetry openTelemetry) {
     return new AwsLambdaFunctionInstrumenter(
@@ -39,4 +39,6 @@ public class AwsLambdaEventsInstrumenterFactory {
     }
     return name == null ? input.getAwsContext().getFunctionName() : name;
   }
+
+  private AwsLambdaEventsInstrumenterFactory() {}
 }

instrumentation/aws-lambda/aws-lambda-events-2.2/library/src/main/java/io/opentelemetry/instrumentation/awslambdaevents/v2_2/internal/AwsLambdaSqsInstrumenterFactory.java

@@ -15,7 +15,7 @@ import io.opentelemetry.instrumentation.api.instrumenter.SpanKindExtractor;
  * This class is internal and is hence not for public use. Its APIs are unstable and can change at
  * any time.
  */
-public class AwsLambdaSqsInstrumenterFactory {
+public final class AwsLambdaSqsInstrumenterFactory {
 
   public static Instrumenter<SQSEvent, Void> forEvent(OpenTelemetry openTelemetry) {
     return Instrumenter.<SQSEvent, Void>builder(
@@ -55,4 +55,6 @@ public class AwsLambdaSqsInstrumenterFactory {
 
     return source + " process";
   }
+
+  private AwsLambdaSqsInstrumenterFactory() {}
 }

instrumentation/azure-core/azure-core-1.14/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/azurecore/v1_14/AzureHttpClientInstrumentation.java

@@ -36,6 +36,7 @@ public class AzureHttpClientInstrumentation implements TypeInstrumentation {
         this.getClass().getName() + "$SuppressNestedClientAdvice");
   }
 
+  @SuppressWarnings("unused")
   public static class SuppressNestedClientAdvice {
 
     @Advice.OnMethodExit(suppress = Throwable.class)

instrumentation/azure-core/azure-core-1.19/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/azurecore/v1_19/AzureHttpClientInstrumentation.java

@@ -36,6 +36,7 @@ public class AzureHttpClientInstrumentation implements TypeInstrumentation {
         this.getClass().getName() + "$SuppressNestedClientAdvice");
   }
 
+  @SuppressWarnings("unused")
   public static class SuppressNestedClientAdvice {
 
     @Advice.OnMethodExit(suppress = Throwable.class)

instrumentation/external-annotations/javaagent/src/test/java/OuterClass.java

@@ -14,4 +14,6 @@ public class OuterClass {
   @Retention(RUNTIME)
   @Target(METHOD)
   public @interface InterestingMethod {}
+
+  private OuterClass() {}
 }

instrumentation/internal/internal-class-loader/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/internal/classloader/BootDelegationInstrumentation.java

@@ -72,6 +72,7 @@ public class BootDelegationInstrumentation implements TypeInstrumentation {
   }
 
   public static class Holder {
+
     public static final List<String> bootstrapPackagesPrefixes = findBootstrapPackagePrefixes();
 
     /**
@@ -95,6 +96,8 @@ public class BootDelegationInstrumentation implements TypeInstrumentation {
         return Constants.BOOTSTRAP_PACKAGE_PREFIXES;
       }
     }
+
+    private Holder() {}
   }
 
   @SuppressWarnings("unused")

instrumentation/internal/internal-class-loader/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/internal/classloader/DefineClassInstrumentation.java

@@ -36,7 +36,7 @@ public class DefineClassInstrumentation implements TypeInstrumentation {
     transformer.applyAdviceToMethod(
         named("defineClass")
             .and(takesArguments(String.class, ByteBuffer.class, ProtectionDomain.class)),
-        DefineClassInstrumentation.class.getName() + "$DefineClassAdvice2");
+        DefineClassInstrumentation.class.getName() + "$DefineClassWithThreeArgsAdvice");
   }
 
   @SuppressWarnings("unused")
@@ -59,7 +59,7 @@ public class DefineClassInstrumentation implements TypeInstrumentation {
   }
 
   @SuppressWarnings("unused")
-  public static class DefineClassAdvice2 {
+  public static class DefineClassWithThreeArgsAdvice {
     @Advice.OnMethodEnter(suppress = Throwable.class)
     public static DefineClassContext onEnter(
         @Advice.This ClassLoader classLoader,

instrumentation/internal/internal-lambda/javaagent/src/test/java/TestLambda.java

@@ -4,7 +4,10 @@
  */
 
 public class TestLambda {
+
   static Runnable makeRunnable() {
     return () -> {};
   }
+
+  private TestLambda() {}
 }

instrumentation/internal/internal-reflection/javaagent-integration-tests/src/main/java/instrumentation/TestTypeInstrumentation.java

@@ -26,7 +26,7 @@ public class TestTypeInstrumentation implements TypeInstrumentation {
     transformer.applyAdviceToMethod(
         named("testMethod"), TestTypeInstrumentation.class.getName() + "$TestAdvice");
     transformer.applyAdviceToMethod(
-        named("testMethod2"), TestTypeInstrumentation.class.getName() + "$TestAdvice2");
+        named("testMethod2"), TestTypeInstrumentation.class.getName() + "$Test2Advice");
   }
 
   @SuppressWarnings("unused")
@@ -41,7 +41,7 @@ public class TestTypeInstrumentation implements TypeInstrumentation {
   }
 
   @SuppressWarnings("unused")
-  public static class TestAdvice2 {
+  public static class Test2Advice {
 
     @Advice.OnMethodExit
     public static void methodExit(

instrumentation/internal/internal-url-class-loader/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/internal/urlclassloader/UrlClassLoaderInstrumentation.java

@@ -38,11 +38,11 @@ public class UrlClassLoaderInstrumentation implements TypeInstrumentation {
             .and(takesArgument(0, URL.class))
             .and(isProtected())
             .and(not(isStatic())),
-        UrlClassLoaderInstrumentation.class.getName() + "$InvalidateClassLoaderMatcher");
+        UrlClassLoaderInstrumentation.class.getName() + "$AddUrlAdvice");
   }
 
   @SuppressWarnings("unused")
-  public static class InvalidateClassLoaderMatcher {
+  public static class AddUrlAdvice {
     @Advice.OnMethodExit(suppress = Throwable.class)
     public static void onExit(@Advice.This URLClassLoader loader) {
       ClassLoaderMatcherCacheHolder.invalidateAllCachesForClassLoader(loader);

instrumentation/jaxrs/jaxrs-1.0/javaagent/src/test/java/JavaInterfaces.java

@@ -66,4 +66,6 @@ public class JavaInterfaces {
       // do nothing
     }
   }
+
+  private JavaInterfaces() {}
 }

instrumentation/jaxrs/jaxrs-2.0/jaxrs-2.0-annotations/javaagent/src/test/java/JavaInterfaces.java

@@ -66,4 +66,6 @@ public class JavaInterfaces {
       // do nothing
     }
   }
+
+  private JavaInterfaces() {}
 }

instrumentation/jaxrs/jaxrs-3.0/jaxrs-3.0-annotations/javaagent/src/test/java/JavaInterfaces.java

@@ -66,4 +66,6 @@ public class JavaInterfaces {
       // do nothing
     }
   }
+
+  private JavaInterfaces() {}
 }

instrumentation/jboss-logmanager/jboss-logmanager-mdc-1.1/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/jbosslogmanager/mdc/v1_1/JbossExtLogRecordInstrumentation.java

@@ -89,6 +89,7 @@ public class JbossExtLogRecordInstrumentation implements TypeInstrumentation {
     }
   }
 
+  @SuppressWarnings("unused")
   public static class GetMdcCopyAdvice {
 
     @Advice.OnMethodExit(suppress = Throwable.class)

instrumentation/jdbc/javaagent/src/test/java/io/opentelemetry/javaagent/instrumentation/jdbc/test/ProxyStatementFactory.java

@@ -9,7 +9,7 @@ import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.Proxy;
 import java.sql.Statement;
 
-public class ProxyStatementFactory {
+public final class ProxyStatementFactory {
 
   public static Statement proxyStatement(Statement statement) throws Exception {
     TestClassLoader classLoader = new TestClassLoader(ProxyStatementFactory.class.getClassLoader());
@@ -33,4 +33,6 @@ public class ProxyStatementFactory {
 
     return proxyStatement;
   }
+
+  private ProxyStatementFactory() {}
 }

instrumentation/jdbc/library/src/main/java/io/opentelemetry/instrumentation/jdbc/internal/DataSourceSingletons.java

@@ -35,4 +35,6 @@ public final class DataSourceSingletons {
   public static Instrumenter<DataSource, Void> instrumenter() {
     return INSTRUMENTER;
   }
+
+  private DataSourceSingletons() {}
 }

instrumentation/jetty/jetty-8.0/javaagent/src/test/java/JavaLambdaMaker.java

@@ -9,4 +9,6 @@ public class JavaLambdaMaker {
   public static Runnable lambda(Runnable runnable) {
     return runnable::run;
   }
+
+  private JavaLambdaMaker() {}
 }

instrumentation/jsp-2.3/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/jsp/JspCompilationContextInstrumentation.java

@@ -31,11 +31,11 @@ public class JspCompilationContextInstrumentation implements TypeInstrumentation
   public void transform(TypeTransformer transformer) {
     transformer.applyAdviceToMethod(
         named("compile").and(takesArguments(0)).and(isPublic()),
-        JspCompilationContextInstrumentation.class.getName() + "$JasperJspCompilationContext");
+        JspCompilationContextInstrumentation.class.getName() + "$CompileAdvice");
   }
 
   @SuppressWarnings("unused")
-  public static class JasperJspCompilationContext {
+  public static class CompileAdvice {
 
     @Advice.OnMethodEnter(suppress = Throwable.class)
     public static void onEnter(

instrumentation/lettuce/lettuce-4.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/lettuce/v4_0/InstrumentationPoints.java

@@ -75,4 +75,6 @@ public final class InstrumentationPoints {
   private static boolean isNonInstrumentingKeyword(ProtocolKeyword keyword) {
     return keyword == SEGFAULT;
   }
+
+  private InstrumentationPoints() {}
 }

instrumentation/lettuce/lettuce-5.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/lettuce/v5_0/LettuceInstrumentationUtil.java

@@ -11,7 +11,7 @@ import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 
-public class LettuceInstrumentationUtil {
+public final class LettuceInstrumentationUtil {
 
   private static final Set<String> nonInstrumentingCommands =
       Collections.unmodifiableSet(
@@ -46,4 +46,6 @@ public class LettuceInstrumentationUtil {
     }
     return commandName;
   }
+
+  private LettuceInstrumentationUtil() {}
 }

instrumentation/logback/logback-appender-1.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/logback/appender/v1_0/LogbackSingletons.java

@@ -11,7 +11,7 @@ import io.opentelemetry.instrumentation.logback.appender.v1_0.internal.LoggingEv
 import io.opentelemetry.javaagent.bootstrap.internal.InstrumentationConfig;
 import java.util.List;
 
-public class LogbackSingletons {
+public final class LogbackSingletons {
 
   private static final LoggingEventMapper mapper;
 
@@ -32,4 +32,6 @@ public class LogbackSingletons {
   public static LoggingEventMapper mapper() {
     return mapper;
   }
+
+  private LogbackSingletons() {}
 }

instrumentation/mongo/mongo-3.1/library/src/main/java/io/opentelemetry/instrumentation/mongo/v3_1/MongoInstrumenterFactory.java

@@ -35,4 +35,6 @@ class MongoInstrumenterFactory {
         .addAttributesExtractor(attributesExtractor)
         .buildInstrumenter(SpanKindExtractor.alwaysClient());
   }
+
+  private MongoInstrumenterFactory() {}
 }

instrumentation/mongo/mongo-4.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/mongo/v4_0/DefaultConnectionPoolInstrumentation.java

@@ -31,6 +31,7 @@ public class DefaultConnectionPoolInstrumentation implements TypeInstrumentation
         this.getClass().getName() + "$SingleResultCallbackAdvice");
   }
 
+  @SuppressWarnings("unused")
   public static class SingleResultCallbackAdvice {
 
     @Advice.OnMethodEnter(suppress = Throwable.class)

instrumentation/netty/netty-3.8/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/netty/v3_8/ChannelPipelineUtil.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.instrumentation.netty.v3_8;
+
+import io.opentelemetry.javaagent.instrumentation.netty.v3_8.client.HttpClientRequestTracingHandler;
+import io.opentelemetry.javaagent.instrumentation.netty.v3_8.client.HttpClientResponseTracingHandler;
+import io.opentelemetry.javaagent.instrumentation.netty.v3_8.client.HttpClientTracingHandler;
+import io.opentelemetry.javaagent.instrumentation.netty.v3_8.server.HttpServerRequestTracingHandler;
+import io.opentelemetry.javaagent.instrumentation.netty.v3_8.server.HttpServerResponseTracingHandler;
+import io.opentelemetry.javaagent.instrumentation.netty.v3_8.server.HttpServerTracingHandler;
+import org.jboss.netty.channel.ChannelHandler;
+import org.jboss.netty.channel.ChannelPipeline;
+import org.jboss.netty.handler.codec.http.HttpClientCodec;
+import org.jboss.netty.handler.codec.http.HttpRequestDecoder;
+import org.jboss.netty.handler.codec.http.HttpRequestEncoder;
+import org.jboss.netty.handler.codec.http.HttpResponseDecoder;
+import org.jboss.netty.handler.codec.http.HttpResponseEncoder;
+import org.jboss.netty.handler.codec.http.HttpServerCodec;
+
+/**
+ * When certain handlers are added to the pipeline, we want to add our corresponding tracing
+ * handlers. If those handlers are later removed, we may want to remove our handlers. That is not
+ * currently implemented.
+ */
+public final class ChannelPipelineUtil {
+
+  public static void wrapHandler(ChannelPipeline pipeline, ChannelHandler handler) {
+    // Server pipeline handlers
+    if (handler instanceof HttpServerCodec) {
+      pipeline.addLast(HttpServerTracingHandler.class.getName(), new HttpServerTracingHandler());
+    } else if (handler instanceof HttpRequestDecoder) {
+      pipeline.addLast(
+          HttpServerRequestTracingHandler.class.getName(), new HttpServerRequestTracingHandler());
+    } else if (handler instanceof HttpResponseEncoder) {
+      pipeline.addLast(
+          HttpServerResponseTracingHandler.class.getName(), new HttpServerResponseTracingHandler());
+    } else
+    // Client pipeline handlers
+    if (handler instanceof HttpClientCodec) {
+      pipeline.addLast(HttpClientTracingHandler.class.getName(), new HttpClientTracingHandler());
+    } else if (handler instanceof HttpRequestEncoder) {
+      pipeline.addLast(
+          HttpClientRequestTracingHandler.class.getName(), new HttpClientRequestTracingHandler());
+    } else if (handler instanceof HttpResponseDecoder) {
+      pipeline.addLast(
+          HttpClientResponseTracingHandler.class.getName(), new HttpClientResponseTracingHandler());
+    }
+  }
+
+  private ChannelPipelineUtil() {}
+}

instrumentation/netty/netty-3.8/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/netty/v3_8/NettyChannelPipelineInstrumentation.java

@@ -15,23 +15,11 @@ import static net.bytebuddy.matcher.ElementMatchers.takesArgument;
 import io.opentelemetry.javaagent.bootstrap.CallDepth;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
-import io.opentelemetry.javaagent.instrumentation.netty.v3_8.client.HttpClientRequestTracingHandler;
-import io.opentelemetry.javaagent.instrumentation.netty.v3_8.client.HttpClientResponseTracingHandler;
-import io.opentelemetry.javaagent.instrumentation.netty.v3_8.client.HttpClientTracingHandler;
-import io.opentelemetry.javaagent.instrumentation.netty.v3_8.server.HttpServerRequestTracingHandler;
-import io.opentelemetry.javaagent.instrumentation.netty.v3_8.server.HttpServerResponseTracingHandler;
-import io.opentelemetry.javaagent.instrumentation.netty.v3_8.server.HttpServerTracingHandler;
 import net.bytebuddy.asm.Advice;
 import net.bytebuddy.description.type.TypeDescription;
 import net.bytebuddy.matcher.ElementMatcher;
 import org.jboss.netty.channel.ChannelHandler;
 import org.jboss.netty.channel.ChannelPipeline;
-import org.jboss.netty.handler.codec.http.HttpClientCodec;
-import org.jboss.netty.handler.codec.http.HttpRequestDecoder;
-import org.jboss.netty.handler.codec.http.HttpRequestEncoder;
-import org.jboss.netty.handler.codec.http.HttpResponseDecoder;
-import org.jboss.netty.handler.codec.http.HttpResponseEncoder;
-import org.jboss.netty.handler.codec.http.HttpServerCodec;
 
 public class NettyChannelPipelineInstrumentation implements TypeInstrumentation {
 
@@ -59,38 +47,6 @@ public class NettyChannelPipelineInstrumentation implements TypeInstrumentation
         NettyChannelPipelineInstrumentation.class.getName() + "$ChannelPipelineAdd3ArgsAdvice");
   }
 
-  /**
-   * When certain handlers are added to the pipeline, we want to add our corresponding tracing
-   * handlers. If those handlers are later removed, we may want to remove our handlers. That is not
-   * currently implemented.
-   */
-  public static class ChannelPipelineAdviceUtil {
-    public static void wrapHandler(ChannelPipeline pipeline, ChannelHandler handler) {
-      // Server pipeline handlers
-      if (handler instanceof HttpServerCodec) {
-        pipeline.addLast(HttpServerTracingHandler.class.getName(), new HttpServerTracingHandler());
-      } else if (handler instanceof HttpRequestDecoder) {
-        pipeline.addLast(
-            HttpServerRequestTracingHandler.class.getName(), new HttpServerRequestTracingHandler());
-      } else if (handler instanceof HttpResponseEncoder) {
-        pipeline.addLast(
-            HttpServerResponseTracingHandler.class.getName(),
-            new HttpServerResponseTracingHandler());
-      } else
-      // Client pipeline handlers
-      if (handler instanceof HttpClientCodec) {
-        pipeline.addLast(HttpClientTracingHandler.class.getName(), new HttpClientTracingHandler());
-      } else if (handler instanceof HttpRequestEncoder) {
-        pipeline.addLast(
-            HttpClientRequestTracingHandler.class.getName(), new HttpClientRequestTracingHandler());
-      } else if (handler instanceof HttpResponseDecoder) {
-        pipeline.addLast(
-            HttpClientResponseTracingHandler.class.getName(),
-            new HttpClientResponseTracingHandler());
-      }
-    }
-  }
-
   @SuppressWarnings("unused")
   public static class ChannelPipelineAdd2ArgsAdvice {
 
@@ -118,7 +74,7 @@ public class NettyChannelPipelineInstrumentation implements TypeInstrumentation
         return;
       }
 
-      ChannelPipelineAdviceUtil.wrapHandler(pipeline, handler);
+      ChannelPipelineUtil.wrapHandler(pipeline, handler);
     }
   }
 
@@ -149,7 +105,7 @@ public class NettyChannelPipelineInstrumentation implements TypeInstrumentation
         return;
       }
 
-      ChannelPipelineAdviceUtil.wrapHandler(pipeline, handler);
+      ChannelPipelineUtil.wrapHandler(pipeline, handler);
     }
   }
 }

instrumentation/netty/netty-4.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/netty/v4_0/AttributeKeys.java

@@ -58,4 +58,6 @@ public class AttributeKeys {
     ConcurrentMap<String, AttributeKey<?>> classLoaderMap = mapSupplier.get(AttributeKey.class);
     return (AttributeKey<T>) classLoaderMap.computeIfAbsent(key, AttributeKey::new);
   }
+
+  private AttributeKeys() {}
 }

instrumentation/opentelemetry-api/opentelemetry-api-1.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/opentelemetryapi/trace/Bridging.java

@@ -160,4 +160,6 @@ public class Bridging {
     applicationTraceState.forEach(agentTraceState::put);
     return agentTraceState.build();
   }
+
+  private Bridging() {}
 }

instrumentation/opentelemetry-api/opentelemetry-api-1.10/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/opentelemetryapi/v1_10/OpenTelemetryInstrumentation.java

@@ -27,7 +27,7 @@ public class OpenTelemetryInstrumentation implements TypeInstrumentation {
         none(), OpenTelemetryInstrumentation.class.getName() + "$InitAdvice");
   }
 
-  @SuppressWarnings({"unused", "ReturnValueIgnored"})
+  @SuppressWarnings({"ReturnValueIgnored", "unused"})
   public static class InitAdvice {
     @Advice.OnMethodEnter
     public static void init() {

instrumentation/opentelemetry-api/opentelemetry-api-1.4/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/opentelemetryapi/v1_4/OpenTelemetryInstrumentation.java

@@ -28,7 +28,7 @@ public class OpenTelemetryInstrumentation implements TypeInstrumentation {
         none(), OpenTelemetryInstrumentation.class.getName() + "$InitAdvice");
   }
 
-  @SuppressWarnings({"unused", "ReturnValueIgnored"})
+  @SuppressWarnings({"ReturnValueIgnored", "unused"})
   public static class InitAdvice {
     @Advice.OnMethodEnter
     public static void init() {

instrumentation/opentelemetry-extension-annotations-1.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/extensionannotations/WithSpanSingletons.java

@@ -18,6 +18,7 @@ import java.lang.reflect.Method;
 import java.util.logging.Logger;
 
 public final class WithSpanSingletons {
+
   private static final String INSTRUMENTATION_NAME =
       "io.opentelemetry.opentelemetry-extension-annotations-1.0";
 
@@ -90,4 +91,6 @@ public final class WithSpanSingletons {
     }
     return spanName;
   }
+
+  private WithSpanSingletons() {}
 }

instrumentation/opentelemetry-instrumentation-annotations-1.16/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/instrumentationannotations/WithSpanSingletons.java

@@ -18,6 +18,7 @@ import java.lang.reflect.Method;
 import java.util.logging.Logger;
 
 public final class WithSpanSingletons {
+
   private static final String INSTRUMENTATION_NAME =
       "io.opentelemetry.opentelemetry-instrumentation-annotations-1.16";
 
@@ -90,4 +91,6 @@ public final class WithSpanSingletons {
     }
     return spanName;
   }
+
+  private WithSpanSingletons() {}
 }

instrumentation/opentelemetry-instrumentation-api/testing/src/main/java/io/opentelemetry/javaagent/instrumentation/testing/AgentSpanTesting.java

@@ -7,7 +7,7 @@ package io.opentelemetry.javaagent.instrumentation.testing;
 
 import io.opentelemetry.instrumentation.api.internal.SpanKey;
 
-public class AgentSpanTesting {
+public final class AgentSpanTesting {
 
   /**
    * Runs the provided {@code runnable} inside the scope of an SERVER span with name {@code
@@ -24,4 +24,6 @@ public class AgentSpanTesting {
   public static void runWithAllSpanKeys(String spanName, Runnable runnable) {
     runnable.run();
   }
+
+  private AgentSpanTesting() {}
 }

instrumentation/play/play-mvc/play-mvc-2.6/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/play/v2_6/ResponseFutureWrapper.java

@@ -13,7 +13,7 @@ import scala.concurrent.ExecutionContext;
 import scala.concurrent.Future;
 import scala.runtime.AbstractFunction1;
 
-public class ResponseFutureWrapper {
+public final class ResponseFutureWrapper {
 
   public static Future<Result> wrap(
       Future<Result> future, Context context, ExecutionContext executionContext) {
@@ -35,4 +35,6 @@ public class ResponseFutureWrapper {
         },
         executionContext);
   }
+
+  private ResponseFutureWrapper() {}
 }

instrumentation/rabbitmq-2.7/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/rabbitmq/RabbitCommandInstrumentation.java

@@ -39,8 +39,11 @@ public class RabbitCommandInstrumentation implements TypeInstrumentation {
         RabbitCommandInstrumentation.class.getName() + "$CommandConstructorAdvice");
   }
 
-  public static class SpanHolder {
+  public static final class SpanHolder {
+
     public static final ThreadLocal<Context> CURRENT_RABBIT_CONTEXT = new ThreadLocal<>();
+
+    private SpanHolder() {}
   }
 
   @SuppressWarnings("unused")

instrumentation/rabbitmq-2.7/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/rabbitmq/RabbitSingletons.java

@@ -20,7 +20,8 @@ import io.opentelemetry.javaagent.bootstrap.internal.InstrumentationConfig;
 import java.util.ArrayList;
 import java.util.List;
 
-public class RabbitSingletons {
+public final class RabbitSingletons {
+
   private static final boolean CAPTURE_EXPERIMENTAL_SPAN_ATTRIBUTES =
       InstrumentationConfig.get()
           .getBoolean("otel.instrumentation.rabbitmq.experimental-span-attributes", false);
@@ -91,4 +92,6 @@ public class RabbitSingletons {
         .addAttributesExtractors(extractors)
         .buildConsumerInstrumenter(DeliveryRequestGetter.INSTANCE);
   }
+
+  private RabbitSingletons() {}
 }

instrumentation/restlet/restlet-2.0/library/src/main/java/io/opentelemetry/instrumentation/restlet/v2_0/internal/RestletInstrumenterFactory.java

@@ -21,7 +21,7 @@ import org.restlet.Response;
  * This class is internal and is hence not for public use. Its APIs are unstable and can change at
  * any time.
  */
-public class RestletInstrumenterFactory {
+public final class RestletInstrumenterFactory {
 
   private static final String INSTRUMENTATION_NAME = "io.opentelemetry.restlet-2.0";
 
@@ -42,4 +42,6 @@ public class RestletInstrumenterFactory {
         .addOperationMetrics(HttpServerMetrics.get())
         .buildServerInstrumenter(new RestletHeadersGetter());
   }
+
+  private RestletInstrumenterFactory() {}
 }

instrumentation/rocketmq-client-4.8/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/rocketmq/RocketMqClientHooks.java

@@ -12,6 +12,7 @@ import org.apache.rocketmq.client.hook.ConsumeMessageHook;
 import org.apache.rocketmq.client.hook.SendMessageHook;
 
 public final class RocketMqClientHooks {
+
   private static final RocketMqTelemetry TELEMETRY =
       RocketMqTelemetry.builder(GlobalOpenTelemetry.get())
           .setPropagationEnabled(
@@ -27,4 +28,6 @@ public final class RocketMqClientHooks {
       TELEMETRY.newTracingConsumeMessageHook();
 
   public static final SendMessageHook SEND_MESSAGE_HOOK = TELEMETRY.newTracingSendMessageHook();
+
+  private RocketMqClientHooks() {}
 }

instrumentation/rocketmq-client-4.8/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/rocketmq/RocketMqConsumerInstrumentation.java

@@ -28,10 +28,11 @@ public class RocketMqConsumerInstrumentation implements TypeInstrumentation {
   public void transform(TypeTransformer transformer) {
     transformer.applyAdviceToMethod(
         isMethod().and(named("start")).and(takesArguments(0)),
-        RocketMqConsumerInstrumentation.class.getName() + "$AdviceStart");
+        RocketMqConsumerInstrumentation.class.getName() + "$StartAdvice");
   }
 
-  public static class AdviceStart {
+  @SuppressWarnings("unused")
+  public static class StartAdvice {
     @Advice.OnMethodEnter(suppress = Throwable.class)
     public static void onEnter(
         @Advice.FieldValue(

instrumentation/rocketmq-client-4.8/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/rocketmq/RocketMqProducerInstrumentation.java

@@ -28,10 +28,11 @@ public class RocketMqProducerInstrumentation implements TypeInstrumentation {
   public void transform(TypeTransformer transformer) {
     transformer.applyAdviceToMethod(
         isMethod().and(named("start")).and(takesArguments(0)),
-        RocketMqProducerInstrumentation.class.getName() + "$AdviceStart");
+        RocketMqProducerInstrumentation.class.getName() + "$StartAdvice");
   }
 
-  public static class AdviceStart {
+  @SuppressWarnings("unused")
+  public static class StartAdvice {
     @Advice.OnMethodEnter(suppress = Throwable.class)
     public static void onEnter(
         @Advice.FieldValue(value = "defaultMQProducerImpl", declaringType = DefaultMQProducer.class)

instrumentation/rocketmq-client-4.8/library/src/main/java/io/opentelemetry/instrumentation/rocketmq/RocketMqInstrumenterFactory.java

@@ -110,4 +110,6 @@ class RocketMqInstrumenterFactory {
   private static String spanNameOnReceive(Void unused) {
     return "multiple_sources receive";
   }
+
+  private RocketMqInstrumenterFactory() {}
 }

instrumentation/runtime-metrics/library/src/main/java/io/opentelemetry/instrumentation/runtimemetrics/BufferPools.java

@@ -79,4 +79,6 @@ public final class BufferPools {
       }
     };
   }
+
+  private BufferPools() {}
 }

instrumentation/servlet/servlet-3.0/javaagent/src/test/java/RequestDispatcherServlet.java

@@ -40,4 +40,6 @@ public class RequestDispatcherServlet {
       dispatcher.include(req, resp);
     }
   }
+
+  private RequestDispatcherServlet() {}
 }

instrumentation/servlet/servlet-5.0/javaagent/src/test/java/RequestDispatcherServlet.java

@@ -40,4 +40,6 @@ public class RequestDispatcherServlet {
       dispatcher.include(req, resp);
     }
   }
+
+  private RequestDispatcherServlet() {}
 }

instrumentation/servlet/servlet-common/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/servlet/common/response/HttpServletResponseAdviceHelper.java

@@ -65,4 +65,6 @@ public class HttpServletResponseAdviceHelper {
       instrumenter.end(context, request, null, throwable);
     }
   }
+
+  private HttpServletResponseAdviceHelper() {}
 }

instrumentation/spark-2.3/javaagent/src/test/java/TestSparkJavaApplication.java

@@ -21,4 +21,6 @@ public class TestSparkJavaApplication {
 
     Spark.awaitInitialization();
   }
+
+  private TestSparkJavaApplication() {}
 }

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/OpenTelemetryAutoConfiguration.java

@@ -44,6 +44,8 @@ import org.springframework.expression.spel.standard.SpelExpressionParser;
 @EnableConfigurationProperties({MetricExportProperties.class, SamplerProperties.class})
 public class OpenTelemetryAutoConfiguration {
 
+  public OpenTelemetryAutoConfiguration() {}
+
   @Configuration
   @ConditionalOnMissingBean(OpenTelemetry.class)
   public static class OpenTelemetryBeanConfig {

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/propagators/CompositeTextMapPropagatorFactory.java

@@ -92,4 +92,6 @@ public final class CompositeTextMapPropagatorFactory {
   private static boolean isOnClasspath(String clazz) {
     return ClassUtils.isPresent(clazz, null);
   }
+
+  private CompositeTextMapPropagatorFactory() {}
 }

instrumentation/spring/spring-integration-4.1/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/spring/integration/ApplicationContextInstrumentation.java

@@ -46,6 +46,7 @@ public class ApplicationContextInstrumentation implements TypeInstrumentation {
         ApplicationContextInstrumentation.class.getName() + "$PostProcessBeanFactoryAdvice");
   }
 
+  @SuppressWarnings("unused")
   public static class PostProcessBeanFactoryAdvice {
     @Advice.OnMethodEnter(suppress = Throwable.class)
     public static void onEnter(@Advice.Argument(0) ConfigurableListableBeanFactory beanFactory) {

instrumentation/spring/spring-webflux-5.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/spring/webflux/SpringWebfluxConfig.java

@@ -7,7 +7,7 @@ package io.opentelemetry.javaagent.instrumentation.spring.webflux;
 
 import io.opentelemetry.javaagent.bootstrap.internal.InstrumentationConfig;
 
-public class SpringWebfluxConfig {
+public final class SpringWebfluxConfig {
 
   private static final boolean CAPTURE_EXPERIMENTAL_SPAN_ATTRIBUTES =
       InstrumentationConfig.get()
@@ -16,4 +16,6 @@ public class SpringWebfluxConfig {
   public static boolean captureExperimentalSpanAttributes() {
     return CAPTURE_EXPERIMENTAL_SPAN_ATTRIBUTES;
   }
+
+  private SpringWebfluxConfig() {}
 }

instrumentation/spring/spring-webflux-5.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/spring/webflux/client/WebClientHelper.java

@@ -14,7 +14,7 @@ import io.opentelemetry.javaagent.bootstrap.internal.InstrumentationConfig;
 import java.util.List;
 import org.springframework.web.reactive.function.client.ExchangeFilterFunction;
 
-public class WebClientHelper {
+public final class WebClientHelper {
 
   private static final SpringWebfluxTelemetry INSTRUMENTATION =
       SpringWebfluxTelemetry.builder(GlobalOpenTelemetry.get())
@@ -33,4 +33,6 @@ public class WebClientHelper {
   public static void addFilter(List<ExchangeFilterFunction> exchangeFilterFunctions) {
     INSTRUMENTATION.addClientTracingFilter(exchangeFilterFunctions);
   }
+
+  private WebClientHelper() {}
 }

instrumentation/spring/spring-webflux-5.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/spring/webflux/server/AdviceUtils.java

@@ -13,7 +13,7 @@ import javax.annotation.Nullable;
 import org.springframework.web.server.ServerWebExchange;
 import reactor.core.publisher.Mono;
 
-public class AdviceUtils {
+public final class AdviceUtils {
 
   public static final String ON_SPAN_END = AdviceUtils.class.getName() + ".Context";
 
@@ -53,4 +53,6 @@ public class AdviceUtils {
   interface OnSpanEnd {
     void end(Throwable throwable);
   }
+
+  private AdviceUtils() {}
 }

instrumentation/tomcat/tomcat-10.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/tomcat/v10_0/Tomcat10AttachResponseAdvice.java

@@ -11,6 +11,7 @@ import net.bytebuddy.asm.Advice;
 import org.apache.coyote.Request;
 import org.apache.coyote.Response;
 
+@SuppressWarnings("unused")
 public class Tomcat10AttachResponseAdvice {
 
   @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)

instrumentation/tomcat/tomcat-7.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/tomcat/v7_0/Tomcat7AttachResponseAdvice.java

@@ -11,6 +11,7 @@ import net.bytebuddy.asm.Advice;
 import org.apache.coyote.Request;
 import org.apache.coyote.Response;
 
+@SuppressWarnings("unused")
 public class Tomcat7AttachResponseAdvice {
 
   @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)

instrumentation/twilio-6.6/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/twilio/TwilioSingletons.java

@@ -13,7 +13,7 @@ import io.opentelemetry.instrumentation.api.instrumenter.InstrumenterBuilder;
 import io.opentelemetry.instrumentation.api.util.SpanNames;
 import io.opentelemetry.javaagent.bootstrap.internal.InstrumentationConfig;
 
-public class TwilioSingletons {
+public final class TwilioSingletons {
 
   private static final boolean CAPTURE_EXPERIMENTAL_SPAN_ATTRIBUTES =
       InstrumentationConfig.get()
@@ -23,8 +23,7 @@ public class TwilioSingletons {
 
   static {
     InstrumenterBuilder<String, Object> instrumenterBuilder =
-        Instrumenter.<String, Object>builder(
+        Instrumenter.builder(GlobalOpenTelemetry.get(), "io.opentelemetry.twilio-6.6", str -> str);
-            GlobalOpenTelemetry.get(), "io.opentelemetry.twilio-6.6", str -> str);
 
     if (CAPTURE_EXPERIMENTAL_SPAN_ATTRIBUTES) {
       instrumenterBuilder.addAttributesExtractor(new TwilioExperimentalAttributesExtractor());
@@ -41,4 +40,6 @@ public class TwilioSingletons {
   public static String spanName(Object serviceExecutor, String methodName) {
     return SpanNames.fromMethod(serviceExecutor.getClass(), methodName);
   }
+
+  private TwilioSingletons() {}
 }

instrumentation/vertx/vertx-http-client/vertx-http-client-3.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/vertx/v3_0/client/HttpClientImplInstrumentation.java

@@ -30,6 +30,7 @@ public class HttpClientImplInstrumentation implements TypeInstrumentation {
         isConstructor(), HttpClientImplInstrumentation.class.getName() + "$AttachStateAdvice");
   }
 
+  @SuppressWarnings("unused")
   public static class AttachStateAdvice {
     @Advice.OnMethodExit(suppress = Throwable.class)
     public static void attachHttpClientOptions(

instrumentation/vertx/vertx-http-client/vertx-http-client-3.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/vertx/v3_0/client/HttpRequestImplInstrumentation.java

@@ -45,6 +45,7 @@ public class HttpRequestImplInstrumentation implements TypeInstrumentation {
         HttpRequestImplInstrumentation.class.getName() + "$Vertx37Advice");
   }
 
+  @SuppressWarnings("unused")
   public static class Vertx30Advice {
     @Advice.OnMethodExit(suppress = Throwable.class)
     public static void attachRequestInfo(
@@ -58,10 +59,11 @@ public class HttpRequestImplInstrumentation implements TypeInstrumentation {
           .set(
               request,
               VertxRequestInfo.create(
-                  httpClientOptions != null ? httpClientOptions.isSsl() : false, host, port));
+                  httpClientOptions != null && httpClientOptions.isSsl(), host, port));
     }
   }
 
+  @SuppressWarnings("unused")
   public static class Vertx34Advice {
     @Advice.OnMethodExit(suppress = Throwable.class)
     public static void attachRequestInfo(
@@ -74,6 +76,7 @@ public class HttpRequestImplInstrumentation implements TypeInstrumentation {
     }
   }
 
+  @SuppressWarnings("unused")
   public static class Vertx37Advice {
     @Advice.OnMethodExit(suppress = Throwable.class)
     public static void attachRequestInfo(

javaagent-bootstrap/src/main/java/io/opentelemetry/javaagent/bootstrap/InstrumentationHolder.java

@@ -9,7 +9,7 @@ import java.lang.instrument.Instrumentation;
 import javax.annotation.Nullable;
 
 /** This class serves as an "everywhere accessible" source of {@link Instrumentation} instance. */
-public class InstrumentationHolder {
+public final class InstrumentationHolder {
 
   @Nullable private static volatile Instrumentation instrumentation;
 
@@ -21,4 +21,6 @@ public class InstrumentationHolder {
   public static void setInstrumentation(Instrumentation instrumentation) {
     InstrumentationHolder.instrumentation = instrumentation;
   }
+
+  private InstrumentationHolder() {}
 }

javaagent-bootstrap/src/main/java/io/opentelemetry/javaagent/bootstrap/JavaagentFileHolder.java

@@ -9,8 +9,9 @@ import java.io.File;
 import javax.annotation.Nullable;
 
 // this is currently unused in this repository, but is available for use in distros
+
 /** This class serves as an "everywhere accessible" source of the agent jar file. */
-public class JavaagentFileHolder {
+public final class JavaagentFileHolder {
 
   @Nullable private static volatile File javaagentFile;
 
@@ -22,4 +23,6 @@ public class JavaagentFileHolder {
   public static void setJavaagentFile(File javaagentFile) {
     JavaagentFileHolder.javaagentFile = javaagentFile;
   }
+
+  private JavaagentFileHolder() {}
 }

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/OpenTelemetryInstaller.java

@@ -17,7 +17,7 @@ import io.opentelemetry.sdk.common.CompletableResultCode;
 import io.opentelemetry.sdk.logs.SdkLogEmitterProvider;
 import java.util.Arrays;
 
-public class OpenTelemetryInstaller {
+public final class OpenTelemetryInstaller {
 
   /**
    * Install the {@link OpenTelemetrySdk} using autoconfigure, and return the {@link
@@ -58,4 +58,6 @@ public class OpenTelemetryInstaller {
 
     return autoConfiguredSdk;
   }
+
+  private OpenTelemetryInstaller() {}
 }

javaagent-tooling/src/testExceptionHandler/java/io/opentelemetry/javaagent/tooling/bytebuddy/ExceptionHandlerTest.java

@@ -119,6 +119,7 @@ class ExceptionHandlerTest {
   }
 
   public static class SomeClass {
+
     public static boolean isInstrumented() {
       return false;
     }
@@ -136,5 +137,7 @@ class ExceptionHandlerTest {
       Object o = new Object();
       System.out.println("large stack: " + l + ' ' + i + ' ' + d + ' ' + o);
     }
+
+    private SomeClass() {}
   }
 }

javaagent/src/test/java/io/opentelemetry/javaagent/ClassToInstrument.java

@@ -8,6 +8,9 @@ package io.opentelemetry.javaagent;
 import io.opentracing.contrib.dropwizard.Trace;
 
 public class ClassToInstrument {
+
   @Trace
   public static void someMethod() {}
+
+  protected ClassToInstrument() {}
 }

javaagent/src/test/java/io/opentelemetry/javaagent/IntegrationTestUtils.java

@@ -261,4 +261,6 @@ public class IntegrationTestUtils {
       }
     }
   }
+
+  private IntegrationTestUtils() {}
 }

javaagent/src/test/java/jvmbootstraptest/AgentLoadedChecker.java

@@ -9,6 +9,7 @@ import java.net.URL;
 import java.net.URLClassLoader;
 
 public class AgentLoadedChecker {
+
   public static void main(String[] args) throws ClassNotFoundException {
     // Empty class loader that delegates to bootstrap
     URLClassLoader emptyClassLoader = new URLClassLoader(new URL[] {}, null);
@@ -20,4 +21,6 @@ public class AgentLoadedChecker {
           "Agent loaded into class loader other than bootstrap: " + agentClass.getClassLoader());
     }
   }
+
+  private AgentLoadedChecker() {}
 }

javaagent/src/test/java/jvmbootstraptest/LogLevelChecker.java

@@ -6,6 +6,7 @@
 package jvmbootstraptest;
 
 public class LogLevelChecker {
+
   // returns an exception if logs are not in DEBUG
   public static void main(String[] args) {
 
@@ -16,4 +17,6 @@ public class LogLevelChecker {
       throw new IllegalStateException("debug mode not set");
     }
   }
+
+  private LogLevelChecker() {}
 }

javaagent/src/test/java/jvmbootstraptest/MyClassLoaderIsNotBootstrap.java

@@ -6,10 +6,13 @@
 package jvmbootstraptest;
 
 public class MyClassLoaderIsNotBootstrap {
+
   public static void main(String[] args) {
     if (MyClassLoaderIsNotBootstrap.class.getClassLoader() == null) {
       throw new IllegalStateException(
           "Application level class was loaded by the bootstrap class loader");
     }
   }
+
+  private MyClassLoaderIsNotBootstrap() {}
 }

muzzle/src/test/groovy/io/opentelemetry/javaagent/tooling/muzzle/ReferenceMatcherTest.groovy

@@ -15,7 +15,7 @@ import io.opentelemetry.test.AnotherTestInterface
 import io.opentelemetry.test.TestAbstractSuperClass
 import io.opentelemetry.test.TestInterface
 import muzzle.TestClasses
-import muzzle.TestClasses.MethodBodyAdvice
+import muzzle.TestClasses.Nested
 import org.objectweb.asm.Type
 import spock.lang.Shared
 import spock.lang.Specification
@@ -35,22 +35,22 @@ class ReferenceMatcherTest extends Specification {
   static final TEST_EXTERNAL_INSTRUMENTATION_PACKAGE = "com.external.otel.instrumentation"
 
   @Shared
-  ClassLoader safeClasspath = new URLClassLoader([ClasspathUtils.createJarWithClasses(MethodBodyAdvice.A,
+  ClassLoader safeClasspath = new URLClassLoader([ClasspathUtils.createJarWithClasses(Nested.A,
-    MethodBodyAdvice.B,
+    Nested.B,
-    MethodBodyAdvice.SomeInterface,
+    Nested.SomeInterface,
-    MethodBodyAdvice.SomeImplementation)] as URL[],
+    Nested.SomeImplementation)] as URL[],
     (ClassLoader) null)
 
   @Shared
-  ClassLoader unsafeClasspath = new URLClassLoader([ClasspathUtils.createJarWithClasses(MethodBodyAdvice.A,
+  ClassLoader unsafeClasspath = new URLClassLoader([ClasspathUtils.createJarWithClasses(Nested.A,
-    MethodBodyAdvice.SomeInterface,
+    Nested.SomeInterface,
-    MethodBodyAdvice.SomeImplementation)] as URL[],
+    Nested.SomeImplementation)] as URL[],
     (ClassLoader) null)
 
   def "match safe classpaths"() {
     setup:
     def collector = new ReferenceCollector({ false })
-    collector.collectReferencesFromAdvice(MethodBodyAdvice.name)
+    collector.collectReferencesFromAdvice(TestClasses.MethodBodyAdvice.name)
     def refMatcher = createMatcher(collector.getReferences())
 
     expect:
@@ -60,7 +60,7 @@ class ReferenceMatcherTest extends Specification {
 
   def "matching does not hold a strong reference to classloaders"() {
     expect:
-    MuzzleWeakReferenceTest.classLoaderRefIsGarbageCollected()
+    MuzzleWeakReferenceTestUtil.classLoaderRefIsGarbageCollected()
   }
 
   private static class CountingClassLoader extends URLClassLoader {
@@ -80,14 +80,14 @@ class ReferenceMatcherTest extends Specification {
   def "muzzle type pool caches"() {
     setup:
     def cl = new CountingClassLoader(
-      [ClasspathUtils.createJarWithClasses(MethodBodyAdvice.A,
+      [ClasspathUtils.createJarWithClasses(Nested.A,
-        MethodBodyAdvice.B,
+        Nested.B,
-        MethodBodyAdvice.SomeInterface,
+        Nested.SomeInterface,
-        MethodBodyAdvice.SomeImplementation)] as URL[],
+        Nested.SomeImplementation)] as URL[],
       (ClassLoader) null)
 
     def collector = new ReferenceCollector({ false })
-    collector.collectReferencesFromAdvice(MethodBodyAdvice.name)
+    collector.collectReferencesFromAdvice(Nested.name)
 
     def refMatcher1 = createMatcher(collector.getReferences())
     def refMatcher2 = createMatcher(collector.getReferences())
@@ -113,9 +113,9 @@ class ReferenceMatcherTest extends Specification {
     getMismatchClassSet(mismatches) == expectedMismatches as Set
 
     where:
-    referenceName           | referenceFlag | classToCheck       | expectedMismatches
+    referenceName | referenceFlag | classToCheck | expectedMismatches
-    MethodBodyAdvice.B.name | NON_INTERFACE | MethodBodyAdvice.B | []
+    Nested.B.name | NON_INTERFACE | Nested.B     | []
-    MethodBodyAdvice.B.name | INTERFACE     | MethodBodyAdvice.B | [Mismatch.MissingFlag]
+    Nested.B.name | INTERFACE     | Nested.B     | [Mismatch.MissingFlag]
   }
 
   def "method match #methodTestDesc"() {
@@ -133,14 +133,14 @@ class ReferenceMatcherTest extends Specification {
     getMismatchClassSet(mismatches) == expectedMismatches as Set
 
     where:
-    methodName      | methodDesc                               | methodFlags           | classToCheck                   | expectedMismatches       | methodTestDesc
+    methodName      | methodDesc                               | methodFlags           | classToCheck         | expectedMismatches       | methodTestDesc
-    "method"        | "(Ljava/lang/String;)Ljava/lang/String;" | []                    | MethodBodyAdvice.B             | []                       | "match method declared in class"
+    "method"        | "(Ljava/lang/String;)Ljava/lang/String;" | []                    | Nested.B             | []                       | "match method declared in class"
-    "hashCode"      | "()I"                                    | []                    | MethodBodyAdvice.B             | []                       | "match method declared in superclass"
+    "hashCode"      | "()I"                                    | []                    | Nested.B             | []                       | "match method declared in superclass"
-    "someMethod"    | "()V"                                    | []                    | MethodBodyAdvice.SomeInterface | []                       | "match method declared in interface"
+    "someMethod"    | "()V"                                    | []                    | Nested.SomeInterface | []                       | "match method declared in interface"
-    "privateStuff"  | "()V"                                    | [PRIVATE_OR_HIGHER]   | MethodBodyAdvice.B             | []                       | "match private method"
+    "privateStuff"  | "()V"                                    | [PRIVATE_OR_HIGHER]   | Nested.B             | []                       | "match private method"
-    "privateStuff"  | "()V"                                    | [PROTECTED_OR_HIGHER] | MethodBodyAdvice.B2            | [Mismatch.MissingFlag]   | "fail match private in supertype"
+    "privateStuff"  | "()V"                                    | [PROTECTED_OR_HIGHER] | Nested.B2            | [Mismatch.MissingFlag]   | "fail match private in supertype"
-    "staticMethod"  | "()V"                                    | [NON_STATIC]          | MethodBodyAdvice.B             | [Mismatch.MissingFlag]   | "static method mismatch"
+    "staticMethod"  | "()V"                                    | [NON_STATIC]          | Nested.B             | [Mismatch.MissingFlag]   | "static method mismatch"
-    "missingMethod" | "()V"                                    | []                    | MethodBodyAdvice.B             | [Mismatch.MissingMethod] | "missing method mismatch"
+    "missingMethod" | "()V"                                    | []                    | Nested.B             | [Mismatch.MissingMethod] | "missing method mismatch"
   }
 
   def "field match #fieldTestDesc"() {
@@ -157,15 +157,15 @@ class ReferenceMatcherTest extends Specification {
     getMismatchClassSet(mismatches) == expectedMismatches as Set
 
     where:
-    fieldName        | fieldType                                        | fieldFlags                    | classToCheck                | expectedMismatches      | fieldTestDesc
+    fieldName        | fieldType                              | fieldFlags                    | classToCheck      | expectedMismatches      | fieldTestDesc
-    "missingField"   | "Ljava/lang/String;"                             | []                            | MethodBodyAdvice.A          | [Mismatch.MissingField] | "mismatch missing field"
+    "missingField"   | "Ljava/lang/String;"                   | []                            | Nested.A          | [Mismatch.MissingField] | "mismatch missing field"
-    "privateField"   | "Ljava/lang/String;"                             | []                            | MethodBodyAdvice.A          | [Mismatch.MissingField] | "mismatch field type signature"
+    "privateField"   | "Ljava/lang/String;"                   | []                            | Nested.A          | [Mismatch.MissingField] | "mismatch field type signature"
-    "privateField"   | "Ljava/lang/Object;"                             | [PRIVATE_OR_HIGHER]           | MethodBodyAdvice.A          | []                      | "match private field"
+    "privateField"   | "Ljava/lang/Object;"                   | [PRIVATE_OR_HIGHER]           | Nested.A          | []                      | "match private field"
-    "privateField"   | "Ljava/lang/Object;"                             | [PROTECTED_OR_HIGHER]         | MethodBodyAdvice.A2         | [Mismatch.MissingFlag]  | "mismatch private field in supertype"
+    "privateField"   | "Ljava/lang/Object;"                   | [PROTECTED_OR_HIGHER]         | Nested.A2         | [Mismatch.MissingFlag]  | "mismatch private field in supertype"
-    "protectedField" | "Ljava/lang/Object;"                             | [STATIC]                      | MethodBodyAdvice.A          | [Mismatch.MissingFlag]  | "mismatch static field"
+    "protectedField" | "Ljava/lang/Object;"                   | [STATIC]                      | Nested.A          | [Mismatch.MissingFlag]  | "mismatch static field"
-    "staticB"        | Type.getType(MethodBodyAdvice.B).getDescriptor() | [STATIC, PROTECTED_OR_HIGHER] | MethodBodyAdvice.A          | []                      | "match static field"
+    "staticB"        | Type.getType(Nested.B).getDescriptor() | [STATIC, PROTECTED_OR_HIGHER] | Nested.A          | []                      | "match static field"
-    "number"         | "I"                                              | [PACKAGE_OR_HIGHER]           | MethodBodyAdvice.Primitives | []                      | "match primitive int"
+    "number"         | "I"                                    | [PACKAGE_OR_HIGHER]           | Nested.Primitives | []                      | "match primitive int"
-    "flag"           | "Z"                                              | [PACKAGE_OR_HIGHER]           | MethodBodyAdvice.Primitives | []                      | "match primitive boolean"
+    "flag"           | "Z"                                    | [PACKAGE_OR_HIGHER]           | Nested.Primitives | []                      | "match primitive boolean"
   }
 
   def "should not check abstract #desc helper classes"() {

muzzle/src/test/java/io/opentelemetry/instrumentation/OtherTestHelperClasses.java

@@ -8,7 +8,8 @@ package io.opentelemetry.instrumentation;
 import muzzle.TestClasses;
 
 public class OtherTestHelperClasses {
-  public static class Foo implements TestClasses.MethodBodyAdvice.SomeInterface {
+
+  public static class Foo implements TestClasses.Nested.SomeInterface {
     @Override
     public void someMethod() {}
   }
@@ -30,4 +31,6 @@ public class OtherTestHelperClasses {
 
     abstract int getAnswer();
   }
+
+  private OtherTestHelperClasses() {}
 }

muzzle/src/test/java/io/opentelemetry/instrumentation/TestHelperClasses.java

@@ -10,6 +10,7 @@ import java.util.List;
 import javax.annotation.Nullable;
 
 public class TestHelperClasses {
+
   public static class Helper extends HelperSuperClass implements HelperInterface {
 
     @Override
@@ -59,4 +60,6 @@ public class TestHelperClasses {
       return 12345;
     }
   }
+
+  private TestHelperClasses() {}
 }

muzzle/src/test/java/io/opentelemetry/javaagent/tooling/muzzle/DeclaredFieldTestClass.java

@@ -7,6 +7,7 @@ package io.opentelemetry.javaagent.tooling.muzzle;
 
 @SuppressWarnings("unused")
 public class DeclaredFieldTestClass {
+
   public static class Advice {
     public void instrument() {
       new Helper().foo();
@@ -25,4 +26,6 @@ public class DeclaredFieldTestClass {
   public static class LibraryBaseClass {
     protected Object superField;
   }
+
+  private DeclaredFieldTestClass() {}
 }

muzzle/src/test/java/io/opentelemetry/javaagent/tooling/muzzle/MuzzleWeakReferenceTestUtil.java

@@ -10,9 +10,9 @@ import java.lang.ref.WeakReference;
 import java.net.URL;
 import java.net.URLClassLoader;
 import java.util.Collections;
-import muzzle.TestClasses;
+import muzzle.TestClasses.MethodBodyAdvice;
 
-public class MuzzleWeakReferenceTest {
+public class MuzzleWeakReferenceTestUtil {
 
   // Spock holds strong references to all local variables. For weak reference testing we must create
   // our strong references away from Spock in this java class.
@@ -21,7 +21,7 @@ public class MuzzleWeakReferenceTest {
     ClassLoader loader = new URLClassLoader(new URL[0], null);
     WeakReference<ClassLoader> clRef = new WeakReference<>(loader);
     ReferenceCollector collector = new ReferenceCollector(className -> false);
-    collector.collectReferencesFromAdvice(TestClasses.MethodBodyAdvice.class.getName());
+    collector.collectReferencesFromAdvice(MethodBodyAdvice.class.getName());
     ReferenceMatcher refMatcher =
         new ReferenceMatcher(
             Collections.emptyList(), collector.getReferences(), className -> false);
@@ -30,4 +30,6 @@ public class MuzzleWeakReferenceTest {
     GcUtils.awaitGc(clRef);
     return clRef.get() == null;
   }
+
+  private MuzzleWeakReferenceTestUtil() {}
 }

muzzle/src/test/java/io/opentelemetry/javaagent/tooling/muzzle/ReferenceCollectorTest.java

@@ -29,6 +29,7 @@ import muzzle.TestClasses;
 import muzzle.TestClasses.HelperAdvice;
 import muzzle.TestClasses.LdcAdvice;
 import muzzle.TestClasses.MethodBodyAdvice;
+import muzzle.TestClasses.Nested;
 import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -48,17 +49,17 @@ class ReferenceCollectorTest {
 
     assertThat(references)
         .containsOnlyKeys(
-            MethodBodyAdvice.A.class.getName(),
+            Nested.A.class.getName(),
-            MethodBodyAdvice.B.class.getName(),
+            Nested.B.class.getName(),
-            MethodBodyAdvice.SomeInterface.class.getName(),
+            Nested.SomeInterface.class.getName(),
-            MethodBodyAdvice.SomeImplementation.class.getName());
+            Nested.SomeImplementation.class.getName());
 
-    ClassRef refB = references.get(MethodBodyAdvice.B.class.getName());
+    ClassRef refB = references.get(Nested.B.class.getName());
-    ClassRef refA = references.get(MethodBodyAdvice.A.class.getName());
+    ClassRef refA = references.get(Nested.A.class.getName());
 
     // interface flags
     assertThat(refB.getFlags()).contains(ManifestationFlag.NON_INTERFACE);
-    assertThat(references.get(MethodBodyAdvice.SomeInterface.class.getName()).getFlags())
+    assertThat(references.get(Nested.SomeInterface.class.getName()).getFlags())
         .contains(ManifestationFlag.INTERFACE);
 
     // class access flags
@@ -92,12 +93,12 @@ class ReferenceCollectorTest {
   @Test
   public void protectedRefTest() {
     ReferenceCollector collector = new ReferenceCollector(s -> false);
-    collector.collectReferencesFromAdvice(MethodBodyAdvice.B2.class.getName());
+    collector.collectReferencesFromAdvice(Nested.B2.class.getName());
     collector.prune();
     Map<String, ClassRef> references = collector.getReferences();
 
     assertMethod(
-        references.get(MethodBodyAdvice.B.class.getName()),
+        references.get(Nested.B.class.getName()),
         "protectedMethod",
         "()V",
         PROTECTED_OR_HIGHER,
@@ -111,7 +112,7 @@ class ReferenceCollectorTest {
     collector.prune();
     Map<String, ClassRef> references = collector.getReferences();
 
-    assertThat(references).containsKey(MethodBodyAdvice.A.class.getName());
+    assertThat(references).containsKey(Nested.A.class.getName());
   }
 
   @Test
@@ -121,7 +122,7 @@ class ReferenceCollectorTest {
     collector.prune();
     Map<String, ClassRef> references = collector.getReferences();
 
-    assertThat(references).containsKey(MethodBodyAdvice.A.class.getName());
+    assertThat(references).containsKey(Nested.A.class.getName());
   }
 
   @Test
@@ -131,23 +132,23 @@ class ReferenceCollectorTest {
     collector.prune();
     Map<String, ClassRef> references = collector.getReferences();
 
-    assertThat(references).containsKey("muzzle.TestClasses$MethodBodyAdvice$SomeImplementation");
+    assertThat(references).containsKey("muzzle.TestClasses$Nested$SomeImplementation");
     assertMethod(
-        references.get("muzzle.TestClasses$MethodBodyAdvice$SomeImplementation"),
+        references.get("muzzle.TestClasses$Nested$SomeImplementation"),
         "someMethod",
         "()V",
         PROTECTED_OR_HIGHER,
         OwnershipFlag.NON_STATIC);
-    assertThat(references).containsKey("muzzle.TestClasses$MethodBodyAdvice$B");
+    assertThat(references).containsKey("muzzle.TestClasses$Nested$B");
     assertMethod(
-        references.get("muzzle.TestClasses$MethodBodyAdvice$B"),
+        references.get("muzzle.TestClasses$Nested$B"),
         "staticMethod",
         "()V",
         PROTECTED_OR_HIGHER,
         OwnershipFlag.STATIC);
-    assertThat(references).containsKey("muzzle.TestClasses$MethodBodyAdvice$A");
+    assertThat(references).containsKey("muzzle.TestClasses$Nested$A");
     assertMethod(
-        references.get("muzzle.TestClasses$MethodBodyAdvice$A"),
+        references.get("muzzle.TestClasses$Nested$A"),
         "<init>",
         "()V",
         PROTECTED_OR_HIGHER,

muzzle/src/test/java/io/opentelemetry/javaagent/tooling/muzzle/VirtualFieldTestClasses.java

@@ -8,8 +8,9 @@ package io.opentelemetry.javaagent.tooling.muzzle;
 import io.opentelemetry.context.Context;
 import io.opentelemetry.instrumentation.api.util.VirtualField;
 
-@SuppressWarnings("ReturnValueIgnored")
+@SuppressWarnings({"ReturnValueIgnored", "unused"})
 public class VirtualFieldTestClasses {
+
   public static class ValidAdvice {
     public static void advice() {
       Runnable.class.getName();
@@ -71,4 +72,6 @@ public class VirtualFieldTestClasses {
   public static class Key2 {}
 
   public static class State {}
+
+  private VirtualFieldTestClasses() {}
 }

muzzle/src/test/java/muzzle/HelperReferenceWrapperTestClasses.java

@@ -7,6 +7,7 @@ package muzzle;
 
 @SuppressWarnings("unused")
 public class HelperReferenceWrapperTestClasses {
+
   interface Interface1 {
     void foo();
   }
@@ -24,4 +25,6 @@ public class HelperReferenceWrapperTestClasses {
     @SuppressWarnings("MethodCanBeStatic")
     private void privateMethodsToo() {}
   }
+
+  private HelperReferenceWrapperTestClasses() {}
 }

muzzle/src/test/java/muzzle/TestClasses.java

@@ -13,22 +13,24 @@ import net.bytebuddy.asm.Advice;
 @SuppressWarnings("unused")
 public class TestClasses {
 
-  @SuppressWarnings("ClassNamedLikeTypeParameter")
   public static class MethodBodyAdvice {
-    @SuppressWarnings("ReturnValueIgnored")
     @Advice.OnMethodEnter
+    @SuppressWarnings("ReturnValueIgnored")
     public static void methodBodyAdvice() {
-      A a = new A();
+      Nested.A a = new Nested.A();
-      SomeInterface inter = new SomeImplementation();
+      Nested.SomeInterface inter = new Nested.SomeImplementation();
       inter.someMethod();
       a.publicB.method("foo");
       a.publicB.methodWithPrimitives(false);
       a.publicB.methodWithArrays(new String[0]);
-      B.staticMethod();
+      Nested.B.staticMethod();
-      A.staticB.method("bar");
+      Nested.A.staticB.method("bar");
       new int[0].clone();
     }
+  }
 
+  @SuppressWarnings("ClassNamedLikeTypeParameter")
+  public static class Nested {
     public static class A {
       public B publicB = new B();
       protected Object protectedField = null;
@@ -85,6 +87,8 @@ public class TestClasses {
     }
 
     public interface AnotherInterface extends SomeInterface {}
+
+    private Nested() {}
   }
 
   public abstract static class BaseClassWithConstructor {
@@ -94,21 +98,20 @@ public class TestClasses {
   public static class LdcAdvice {
     @SuppressWarnings("ReturnValueIgnored")
     public static void ldcMethod() {
-      MethodBodyAdvice.A.class.getName();
+      Nested.A.class.getName();
     }
   }
 
   public static class InstanceofAdvice {
     public static boolean instanceofMethod(Object a) {
-      return a instanceof MethodBodyAdvice.A;
+      return a instanceof Nested.A;
     }
   }
 
   public static class InvokeDynamicAdvice {
-    public static MethodBodyAdvice.SomeInterface invokeDynamicMethod(
+    public static Nested.SomeInterface invokeDynamicMethod(Nested.SomeImplementation a) {
-        MethodBodyAdvice.SomeImplementation a) {
+      Runnable staticMethod = Nested.B::staticMethod;
-      Runnable staticMethod = MethodBodyAdvice.B::staticMethod;
+      Runnable constructorMethod = Nested.A::new;
-      Runnable constructorMethod = MethodBodyAdvice.A::new;
       return a::someMethod;
     }
   }
@@ -130,4 +133,6 @@ public class TestClasses {
       new ExternalHelper().instrument();
     }
   }
+
+  private TestClasses() {}
 }

smoke-tests/images/fake-backend/src/main/java/io/opentelemetry/smoketest/fakebackend/FakeBackendMain.java

@@ -127,4 +127,6 @@ public class FakeBackendMain {
     server.start().join();
     Runtime.getRuntime().addShutdownHook(new Thread(() -> server.stop().join()));
   }
+
+  private FakeBackendMain() {}
 }

smoke-tests/images/grpc/src/main/java/io/opentelemetry/smoketest/grpc/TestMain.java

@@ -22,4 +22,6 @@ public class TestMain {
     logger.info("Server started at port 8080.");
     server.awaitTermination();
   }
+
+  private TestMain() {}
 }

smoke-tests/images/spring-boot/src/main/java/io/opentelemetry/smoketest/springboot/SpringbootApplication.java

@@ -14,4 +14,6 @@ public class SpringbootApplication {
   public static void main(String[] args) {
     SpringApplication.run(SpringbootApplication.class, args);
   }
+
+  private SpringbootApplication() {}
 }

testing/agent-exporter/src/main/java/io/opentelemetry/javaagent/testing/exporter/AgentTestingExporterFactory.java

@@ -8,7 +8,7 @@ package io.opentelemetry.javaagent.testing.exporter;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 
-public class AgentTestingExporterFactory {
+public final class AgentTestingExporterFactory {
 
   static final OtlpInMemorySpanExporter spanExporter = new OtlpInMemorySpanExporter();
   static final OtlpInMemoryMetricExporter metricExporter = new OtlpInMemoryMetricExporter();
@@ -38,4 +38,6 @@ public class AgentTestingExporterFactory {
   public static boolean forceFlushCalled() {
     return AgentTestingCustomizer.spanProcessor.forceFlushCalled;
   }
+
+  private AgentTestingExporterFactory() {}
 }