Make public src/main classes final where possible. (#2309)

* Make public src/main classes final where possible.

* methods

* Spot

api/context/src/main/java/io/opentelemetry/context/StrictContextStorage.java

@@ -65,7 +65,7 @@ import java.util.stream.Collectors;
  * > }
  * }</pre>
  */
-public class StrictContextStorage implements ContextStorage {
+public final class StrictContextStorage implements ContextStorage {
 
   /**
    * Returns a new {@link StrictContextStorage} which delegates to the provided {@link

exporters/jaeger-thrift/src/main/java/io/opentelemetry/exporter/jaeger/thrift/JaegerThriftSpanExporter.java

@@ -144,4 +144,9 @@ public final class JaegerThriftSpanExporter implements SpanExporter {
     // todo
     return result.succeed();
   }
+
+  // Visible for testing
+  Process getProcess() {
+    return process;
+  }
 }

exporters/jaeger-thrift/src/main/java/io/opentelemetry/exporter/jaeger/thrift/JaegerThriftSpanExporterBuilder.java

@@ -11,7 +11,7 @@ import io.opentelemetry.sdk.common.export.ConfigBuilder;
 import java.util.Map;
 
 /** Builder utility for this exporter. */
-public class JaegerThriftSpanExporterBuilder
+public final class JaegerThriftSpanExporterBuilder
     extends ConfigBuilder<JaegerThriftSpanExporterBuilder> {
 
   private static final String KEY_SERVICE_NAME = "otel.exporter.jaeger.service.name";

exporters/jaeger-thrift/src/test/java/io/opentelemetry/exporter/jaeger/thrift/JaegerThriftSpanExporterTest.java

@@ -38,7 +38,6 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.Mock;
-import org.mockito.Mockito;
 import org.mockito.junit.jupiter.MockitoExtension;
 
 @ExtendWith(MockitoExtension.class)
@@ -235,14 +234,12 @@ class JaegerThriftSpanExporterTest {
   void configTest() {
     Map<String, String> options = new HashMap<>();
     String serviceName = "myGreatService";
-    String endpoint = "http://127.0.0.1:9090";
     options.put("otel.exporter.jaeger.service.name", serviceName);
-    options.put("otel.exporter.jaeger.endpoint", endpoint);
+    JaegerThriftSpanExporter exporter =
-    JaegerThriftSpanExporterBuilder config = JaegerThriftSpanExporter.builder();
+        JaegerThriftSpanExporter.builder()
-    JaegerThriftSpanExporterBuilder spy = Mockito.spy(config);
+            .fromConfigMap(options, ConfigBuilderTest.getNaming())
-    spy.fromConfigMap(options, ConfigBuilderTest.getNaming()).build();
+            .build();
-    verify(spy).setServiceName(serviceName);
+    assertThat(exporter.getProcess().getServiceName()).isEqualTo(serviceName);
-    verify(spy).setEndpoint(endpoint);
   }
 
   abstract static class ConfigBuilderTest extends ConfigBuilder<ConfigBuilderTest> {

exporters/jaeger/src/main/java/io/opentelemetry/exporter/jaeger/JaegerGrpcSpanExporter.java

@@ -49,6 +49,7 @@ public final class JaegerGrpcSpanExporter implements SpanExporter {
   private static final String IP_KEY = "ip";
   private static final String IP_DEFAULT = "0.0.0.0";
   private final CollectorServiceGrpc.CollectorServiceFutureStub stub;
+
   private final Model.Process.Builder processBuilder;
   private final ManagedChannel managedChannel;
   private final long deadlineMs;
@@ -208,4 +209,14 @@ public final class JaegerGrpcSpanExporter implements SpanExporter {
     managedChannel.shutdown();
     return result;
   }
+
+  // Visible for testing
+  Model.Process.Builder getProcessBuilder() {
+    return processBuilder;
+  }
+
+  // Visible for testing
+  ManagedChannel getManagedChannel() {
+    return managedChannel;
+  }
 }

exporters/jaeger/src/main/java/io/opentelemetry/exporter/jaeger/JaegerGrpcSpanExporterBuilder.java

@@ -11,7 +11,8 @@ import io.opentelemetry.sdk.common.export.ConfigBuilder;
 import java.util.Map;
 
 /** Builder utility for this exporter. */
-public class JaegerGrpcSpanExporterBuilder extends ConfigBuilder<JaegerGrpcSpanExporterBuilder> {
+public final class JaegerGrpcSpanExporterBuilder
+    extends ConfigBuilder<JaegerGrpcSpanExporterBuilder> {
   private static final String KEY_SERVICE_NAME = "otel.exporter.jaeger.service.name";
   private static final String KEY_ENDPOINT = "otel.exporter.jaeger.endpoint";
 

exporters/jaeger/src/test/java/io/opentelemetry/exporter/jaeger/JaegerGrpcSpanExporterTest.java

@@ -45,7 +45,6 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.mockito.ArgumentCaptor;
 import org.mockito.ArgumentMatchers;
-import org.mockito.Mockito;
 
 class JaegerGrpcSpanExporterTest {
   private static final String TRACE_ID = "00000000000000000000000000abc123";
@@ -264,11 +263,12 @@ class JaegerGrpcSpanExporterTest {
     String endpoint = "127.0.0.1:9090";
     options.put("otel.exporter.jaeger.service.name", serviceName);
     options.put("otel.exporter.jaeger.endpoint", endpoint);
-    JaegerGrpcSpanExporterBuilder config = JaegerGrpcSpanExporter.builder();
+    JaegerGrpcSpanExporter exporter =
-    JaegerGrpcSpanExporterBuilder spy = Mockito.spy(config);
+        JaegerGrpcSpanExporter.builder()
-    spy.fromConfigMap(options, ConfigBuilderTest.getNaming()).build();
+            .fromConfigMap(options, ConfigBuilderTest.getNaming())
-    Mockito.verify(spy).setServiceName(serviceName);
+            .build();
-    Mockito.verify(spy).setEndpoint(endpoint);
+    assertThat(exporter.getProcessBuilder().getServiceName()).isEqualTo(serviceName);
+    assertThat(exporter.getManagedChannel().authority()).isEqualTo(endpoint);
   }
 
   abstract static class ConfigBuilderTest extends ConfigBuilder<ConfigBuilderTest> {

exporters/logging/src/main/java/io/opentelemetry/exporter/logging/LoggingMetricExporter.java

@@ -13,7 +13,7 @@ import java.util.logging.Handler;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
-public class LoggingMetricExporter implements MetricExporter {
+public final class LoggingMetricExporter implements MetricExporter {
   private static final Logger logger = Logger.getLogger(LoggingMetricExporter.class.getName());
 
   @Override

exporters/logging/src/main/java/io/opentelemetry/exporter/logging/LoggingSpanExporter.java

@@ -14,7 +14,7 @@ import java.util.logging.Level;
 import java.util.logging.Logger;
 
 /** A Span Exporter that logs every span at INFO level using java.util.logging. */
-public class LoggingSpanExporter implements SpanExporter {
+public final class LoggingSpanExporter implements SpanExporter {
   private static final Logger logger = Logger.getLogger(LoggingSpanExporter.class.getName());
 
   @Override

exporters/otlp/build.gradle

@@ -18,7 +18,9 @@ dependencies {
             libraries.protobuf,
             libraries.protobuf_util
 
-    testImplementation project(':opentelemetry-sdk-testing')
+    testImplementation project(':opentelemetry-sdk-testing'),
+            'com.linecorp.armeria:armeria-grpc',
+            'com.linecorp.armeria:armeria-junit5'
 
     testImplementation "io.grpc:grpc-testing:${grpcVersion}"
     testRuntime "io.grpc:grpc-netty-shaded:${grpcVersion}"

exporters/otlp/src/main/java/io/opentelemetry/exporter/otlp/OtlpGrpcSpanExporter.java

@@ -75,6 +75,7 @@ public final class OtlpGrpcSpanExporter implements SpanExporter {
       Labels.of("exporter", EXPORTER_NAME, "success", "false");
 
   private final TraceServiceFutureStub traceService;
+
   private final ManagedChannel managedChannel;
   private final long deadlineMs;
   private final LongCounter.BoundLongCounter spansSeen;
@@ -188,4 +189,9 @@ public final class OtlpGrpcSpanExporter implements SpanExporter {
     this.spansExportedFailure.unbind();
     return result;
   }
+
+  // Visible for testing
+  long getDeadlineMs() {
+    return deadlineMs;
+  }
 }

exporters/otlp/src/main/java/io/opentelemetry/exporter/otlp/OtlpGrpcSpanExporterBuilder.java

@@ -18,7 +18,7 @@ import java.util.Map;
 import javax.annotation.Nullable;
 
 /** Builder utility for this exporter. */
-public class OtlpGrpcSpanExporterBuilder extends ConfigBuilder<OtlpGrpcSpanExporterBuilder> {
+public final class OtlpGrpcSpanExporterBuilder extends ConfigBuilder<OtlpGrpcSpanExporterBuilder> {
 
   private static final String KEY_TIMEOUT = "otel.exporter.otlp.span.timeout";
   private static final String KEY_ENDPOINT = "otel.exporter.otlp.span.endpoint";

exporters/otlp/src/test/java/io/opentelemetry/exporter/otlp/OtlpGrpcSpanExporterTest.java

@@ -9,6 +9,11 @@ import static org.assertj.core.api.Assertions.assertThat;
 import static org.awaitility.Awaitility.await;
 
 import com.google.common.io.Closer;
+import com.linecorp.armeria.common.RequestHeaders;
+import com.linecorp.armeria.server.ServerBuilder;
+import com.linecorp.armeria.server.ServiceRequestContext;
+import com.linecorp.armeria.server.grpc.GrpcService;
+import com.linecorp.armeria.testing.junit5.server.ServerExtension;
 import io.grpc.ManagedChannel;
 import io.grpc.Server;
 import io.grpc.Status;
@@ -17,6 +22,8 @@ import io.grpc.inprocess.InProcessChannelBuilder;
 import io.grpc.inprocess.InProcessServerBuilder;
 import io.grpc.stub.StreamObserver;
 import io.opentelemetry.api.trace.Span.Kind;
+import io.opentelemetry.api.trace.SpanId;
+import io.opentelemetry.api.trace.TraceId;
 import io.opentelemetry.proto.collector.trace.v1.ExportTraceServiceRequest;
 import io.opentelemetry.proto.collector.trace.v1.ExportTraceServiceResponse;
 import io.opentelemetry.proto.collector.trace.v1.TraceServiceGrpc;
@@ -26,6 +33,7 @@ import io.opentelemetry.sdk.testing.trace.TestSpanData;
 import io.opentelemetry.sdk.trace.data.SpanData;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -34,9 +42,42 @@ import java.util.concurrent.TimeUnit;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-import org.mockito.Mockito;
+import org.junit.jupiter.api.extension.RegisterExtension;
 
 class OtlpGrpcSpanExporterTest {
+
+  @RegisterExtension
+  public static ServerExtension server =
+      new ServerExtension() {
+        @Override
+        protected void configure(ServerBuilder sb) throws Exception {
+          sb.service(
+              GrpcService.builder()
+                  .addService(
+                      new TraceServiceGrpc.TraceServiceImplBase() {
+                        @Override
+                        public void export(
+                            ExportTraceServiceRequest request,
+                            StreamObserver<ExportTraceServiceResponse> responseObserver) {
+                          RequestHeaders headers =
+                              ServiceRequestContext.current().request().headers();
+                          if (headers.get("key").equals("value")
+                              && headers.get("key2").equals("value2=")
+                              && headers.get("key3").equals("val=ue3")
+                              && headers.get("key4").equals("value4")
+                              && !headers.contains("key5")) {
+                            responseObserver.onNext(
+                                ExportTraceServiceResponse.getDefaultInstance());
+                            responseObserver.onCompleted();
+                          } else {
+                            responseObserver.onError(new AssertionError("Invalid metadata"));
+                          }
+                        }
+                      })
+                  .build());
+        }
+      };
+
   private static final String TRACE_ID = "00000000000000000000000000abc123";
   private static final String SPAN_ID = "0000000000def456";
 
@@ -50,23 +91,36 @@ class OtlpGrpcSpanExporterTest {
   @Test
   void configTest() {
     Map<String, String> options = new HashMap<>();
-    options.put("otel.exporter.otlp.span.timeout", "12");
+    String endpoint = "localhost:" + server.httpPort();
-    options.put("otel.exporter.otlp.span.endpoint", "http://localhost:6553");
+    options.put("otel.exporter.otlp.span.timeout", "5124");
+    options.put("otel.exporter.otlp.span.endpoint", endpoint);
     options.put("otel.exporter.otlp.span.insecure", "true");
     options.put(
         "otel.exporter.otlp.span.headers",
         "key=value;key2=value2=;key3=val=ue3; key4 = value4 ;key5= ");
-    OtlpGrpcSpanExporterBuilder config = OtlpGrpcSpanExporter.builder();
+    OtlpGrpcSpanExporter exporter =
-    OtlpGrpcSpanExporterBuilder spy = Mockito.spy(config);
+        OtlpGrpcSpanExporter.builder()
-    spy.fromConfigMap(options, OtlpGrpcMetricExporterTest.ConfigBuilderTest.getNaming());
+            .fromConfigMap(options, OtlpGrpcMetricExporterTest.ConfigBuilderTest.getNaming())
-    Mockito.verify(spy).setDeadlineMs(12);
+            .build();
-    Mockito.verify(spy).setEndpoint("http://localhost:6553");
+
-    Mockito.verify(spy).setUseTls(false);
+    assertThat(exporter.getDeadlineMs()).isEqualTo(5124);
-    Mockito.verify(spy).addHeader("key", "value");
+    assertThat(
-    Mockito.verify(spy).addHeader("key2", "value2=");
+            exporter
-    Mockito.verify(spy).addHeader("key3", "val=ue3");
+                .export(
-    Mockito.verify(spy).addHeader("key4", "value4");
+                    Arrays.asList(
-    Mockito.verify(spy, Mockito.never()).addHeader("key5", "");
+                        TestSpanData.builder()
+                            .setTraceId(TraceId.getInvalid())
+                            .setSpanId(SpanId.getInvalid())
+                            .setName("name")
+                            .setKind(Kind.CLIENT)
+                            .setStartEpochNanos(1)
+                            .setEndEpochNanos(2)
+                            .setStatus(SpanData.Status.ok())
+                            .setHasEnded(true)
+                            .build()))
+                .join(10, TimeUnit.SECONDS)
+                .isSuccess())
+        .isTrue();
   }
 
   @BeforeEach

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/AwsXRayPropagator.java

@@ -35,7 +35,7 @@ import javax.annotation.Nullable;
  *     .build());
  * }</pre>
  */
-public class AwsXRayPropagator implements TextMapPropagator {
+public final class AwsXRayPropagator implements TextMapPropagator {
 
   // Visible for testing
   static final String TRACE_HEADER_KEY = "X-Amzn-Trace-Id";

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/B3Propagator.java

@@ -46,7 +46,7 @@ import javax.annotation.concurrent.Immutable;
  * }</pre>
  */
 @Immutable
-public class B3Propagator implements TextMapPropagator {
+public final class B3Propagator implements TextMapPropagator {
   static final String TRACE_ID_HEADER = "X-B3-TraceId";
   static final String SPAN_ID_HEADER = "X-B3-SpanId";
   static final String SAMPLED_HEADER = "X-B3-Sampled";

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/JaegerPropagator.java

@@ -31,7 +31,7 @@ import javax.annotation.concurrent.Immutable;
  * Format</a>.
  */
 @Immutable
-public class JaegerPropagator implements TextMapPropagator {
+public final class JaegerPropagator implements TextMapPropagator {
 
   private static final Logger logger = Logger.getLogger(JaegerPropagator.class.getName());
 

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/OtTracerPropagator.java

@@ -26,7 +26,7 @@ import javax.annotation.concurrent.Immutable;
  * TextMapPropagator</a>.
  */
 @Immutable
-public class OtTracerPropagator implements TextMapPropagator {
+public final class OtTracerPropagator implements TextMapPropagator {
 
   static final String TRACE_ID_HEADER = "ot-tracer-traceid";
   static final String SPAN_ID_HEADER = "ot-tracer-spanid";

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/TraceMultiPropagator.java

@@ -50,7 +50,7 @@ import javax.annotation.concurrent.Immutable;
  * }</pre>
  */
 @Immutable
-public class TraceMultiPropagator implements TextMapPropagator {
+public final class TraceMultiPropagator implements TextMapPropagator {
 
   /** Returns a {@link TraceMultiPropagator} for the given {@code propagators}. */
   public static TextMapPropagator create(TextMapPropagator... propagators) {

sdk-extensions/aws/src/main/java/io/opentelemetry/sdk/extension/aws/resource/BeanstalkResource.java

@@ -21,7 +21,7 @@ import java.util.logging.Logger;
  * A {@link ResourceProvider} which provides information about the current EC2 instance if running
  * on AWS Elastic Beanstalk.
  */
-public class BeanstalkResource extends ResourceProvider {
+public final class BeanstalkResource extends ResourceProvider {
 
   private static final Logger logger = Logger.getLogger(BeanstalkResource.class.getName());
 

sdk-extensions/aws/src/main/java/io/opentelemetry/sdk/extension/aws/resource/Ec2Resource.java

@@ -29,7 +29,7 @@ import javax.annotation.Nullable;
  * A {@link ResourceProvider} which provides information about the current EC2 instance if running
  * on AWS EC2.
  */
-public class Ec2Resource extends ResourceProvider {
+public final class Ec2Resource extends ResourceProvider {
 
   private static final Logger logger = Logger.getLogger(Ec2Resource.class.getName());
 

sdk-extensions/aws/src/main/java/io/opentelemetry/sdk/extension/aws/resource/EcsResource.java

@@ -19,7 +19,7 @@ import java.util.logging.Logger;
  * A {@link ResourceProvider} which provides information about the current ECS container if running
  * on AWS ECS.
  */
-public class EcsResource extends ResourceProvider {
+public final class EcsResource extends ResourceProvider {
 
   private static final Logger logger = Logger.getLogger(EcsResource.class.getName());
 

sdk-extensions/aws/src/main/java/io/opentelemetry/sdk/extension/aws/resource/EksResource.java

@@ -21,7 +21,7 @@ import java.util.Map;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
-public class EksResource extends ResourceProvider {
+public final class EksResource extends ResourceProvider {
 
   static final String K8S_SVC_URL = "https://kubernetes.default.svc";
   static final String AUTH_CONFIGMAP_PATH = "/api/v1/namespaces/kube-system/configmaps/aws-auth";

sdk-extensions/aws/src/main/java/io/opentelemetry/sdk/extension/aws/trace/AwsXrayIdGenerator.java

@@ -20,7 +20,7 @@ import java.util.concurrent.TimeUnit;
  *     href="https://docs.aws.amazon.com/xray/latest/devguide/xray-api-sendingdata.html#xray-api-traceids">Generating
  *     Trace IDs</a>
  */
-public class AwsXrayIdGenerator implements IdGenerator {
+public final class AwsXrayIdGenerator implements IdGenerator {
 
   private static final IdGenerator RANDOM_ID_GENERATOR = IdGenerator.random();
 

sdk-extensions/jaeger-remote-sampler/src/main/java/io/opentelemetry/sdk/extension/trace/jaeger/sampler/JaegerRemoteSampler.java

@@ -26,7 +26,7 @@ import java.util.logging.Level;
 import java.util.logging.Logger;
 
 /** Remote sampler that gets sampling configuration from remote Jaeger server. */
-public class JaegerRemoteSampler implements Sampler {
+public final class JaegerRemoteSampler implements Sampler {
   private static final Logger logger = Logger.getLogger(JaegerRemoteSampler.class.getName());
 
   private static final String WORKER_THREAD_NAME =

sdk-extensions/jfr-events/src/main/java/io/opentelemetry/sdk/extension/jfr/JfrContextStorageWrapper.java

@@ -10,7 +10,7 @@ import io.opentelemetry.context.Context;
 import io.opentelemetry.context.ContextStorage;
 import io.opentelemetry.context.Scope;
 
-public class JfrContextStorageWrapper implements ContextStorage {
+public final class JfrContextStorageWrapper implements ContextStorage {
 
   private final ContextStorage wrapped;
 

sdk-extensions/jfr-events/src/main/java/io/opentelemetry/sdk/extension/jfr/JfrSpanProcessor.java

@@ -20,7 +20,7 @@ import io.opentelemetry.sdk.trace.SpanProcessor;
  * other SpanProcessor which may affect timings. When possible, register it first before any other
  * processors to allow the most accurate measurements.
  */
-public class JfrSpanProcessor implements SpanProcessor {
+public final class JfrSpanProcessor implements SpanProcessor {
 
   private final WeakConcurrentMap<SpanContext, SpanEvent> spanEvents =
       new WeakConcurrentMap.WithInlinedExpunction<>();

sdk-extensions/logging/src/main/java/io/opentelemetry/sdk/logging/LogSinkSdkProvider.java

@@ -12,7 +12,7 @@ import java.util.Collection;
 import java.util.List;
 import java.util.Objects;
 
-public class LogSinkSdkProvider {
+public final class LogSinkSdkProvider {
   private final LogSink logSink = new SdkLogSink();
   private final List<LogProcessor> processors = new ArrayList<>();
 

sdk-extensions/logging/src/main/java/io/opentelemetry/sdk/logging/export/BatchLogProcessor.java

@@ -24,7 +24,7 @@ import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 
-public class BatchLogProcessor implements LogProcessor {
+public final class BatchLogProcessor implements LogProcessor {
   private static final String WORKER_THREAD_NAME =
       BatchLogProcessor.class.getSimpleName() + "_WorkerThread";
 

sdk-extensions/resources/src/main/java/io/opentelemetry/sdk/extension/resources/OsResource.java

@@ -12,7 +12,7 @@ import io.opentelemetry.sdk.resources.ResourceProvider;
 import javax.annotation.Nullable;
 
 /** {@link ResourceProvider} which provides information about the current operating system. */
-public class OsResource extends ResourceProvider {
+public final class OsResource extends ResourceProvider {
 
   @Override
   protected Attributes getAttributes() {

sdk-extensions/resources/src/main/java/io/opentelemetry/sdk/extension/resources/ProcessResource.java

@@ -14,7 +14,7 @@ import java.lang.management.ManagementFactory;
 import java.lang.management.RuntimeMXBean;
 
 /** {@link ResourceProvider} which provides information about the current running process. */
-public class ProcessResource extends ResourceProvider {
+public final class ProcessResource extends ResourceProvider {
   @Override
   protected Attributes getAttributes() {
     AttributesBuilder attributes = Attributes.builder();

sdk/all/src/main/java/io/opentelemetry/sdk/OpenTelemetrySdkFactory.java

@@ -12,7 +12,7 @@ import io.opentelemetry.spi.OpenTelemetryFactory;
  * Factory SPI implementation to register a {@link OpenTelemetrySdk} as the default {@link
  * OpenTelemetry}.
  */
-public class OpenTelemetrySdkFactory implements OpenTelemetryFactory {
+public final class OpenTelemetrySdkFactory implements OpenTelemetryFactory {
   @Override
   public OpenTelemetry create() {
     return OpenTelemetrySdk.builder().build();

sdk/common/src/main/java/io/opentelemetry/sdk/common/CompletableResultCode.java

@@ -22,7 +22,7 @@ import javax.annotation.concurrent.GuardedBy;
  * <p>The implementation of Export operations are often asynchronous in nature, hence the need to
  * convey a result at a later time. CompletableResultCode facilitates this.
  */
-public class CompletableResultCode {
+public final class CompletableResultCode {
   /** Returns a {@link CompletableResultCode} that has been completed successfully. */
   public static CompletableResultCode ofSuccess() {
     return SUCCESS;

sdk/common/src/main/java/io/opentelemetry/sdk/internal/DaemonThreadFactory.java

@@ -13,7 +13,7 @@ import java.util.concurrent.atomic.AtomicInteger;
  * A {@link ThreadFactory} that delegates to {@code Executors.defaultThreadFactory()} and marks all
  * threads as daemon.
  */
-public class DaemonThreadFactory implements ThreadFactory {
+public final class DaemonThreadFactory implements ThreadFactory {
   private final String namePrefix;
   private final AtomicInteger counter = new AtomicInteger();
 

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/view/Aggregations.java

@@ -27,7 +27,7 @@ import java.util.Map;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
-public class Aggregations {
+public final class Aggregations {
 
   /**
    * Returns an {@code Aggregation} that calculates sum of recorded measurements.

sdk/testing/src/main/java/io/opentelemetry/sdk/testing/context/SettableContextStorageProvider.java

@@ -14,7 +14,7 @@ import java.util.List;
 import java.util.ServiceLoader;
 
 /** A {@link ContextStorageProvider} which can have it's {@link ContextStorage} set at any time. */
-public class SettableContextStorageProvider implements ContextStorageProvider {
+public final class SettableContextStorageProvider implements ContextStorageProvider {
   @Override
   public ContextStorage get() {
     return SettableContextStorage.INSTANCE;

sdk/testing/src/main/java/io/opentelemetry/sdk/testing/exporter/InMemoryMetricExporter.java

@@ -52,7 +52,7 @@ import java.util.concurrent.LinkedBlockingQueue;
  * }
  * </code></pre>
  */
-public class InMemoryMetricExporter implements MetricExporter {
+public final class InMemoryMetricExporter implements MetricExporter {
 
   // using LinkedBlockingQueue to avoid manual locks for thread-safe operations
   private final Queue<MetricData> finishedMetricItems = new LinkedBlockingQueue<>();

sdk/testing/src/main/java/io/opentelemetry/sdk/testing/junit4/OpenTelemetryRule.java

@@ -42,7 +42,7 @@ import org.junit.rules.ExternalResource;
  * >  }
  * }</pre>
  */
-public class OpenTelemetryRule extends ExternalResource {
+public final class OpenTelemetryRule extends ExternalResource {
 
   /**
    * Returns a {@link OpenTelemetryRule} with a default SDK initialized with an in-memory span
@@ -97,7 +97,7 @@ public class OpenTelemetryRule extends ExternalResource {
   }
 
   @Override
-  protected void before() throws Throwable {
+  protected void before() {
     previousGlobalOpenTelemetry = GlobalOpenTelemetry.get();
     GlobalOpenTelemetry.set(openTelemetry);
     clearSpans();

sdk/testing/src/main/java/io/opentelemetry/sdk/testing/junit5/OpenTelemetryExtension.java

@@ -47,7 +47,7 @@ import org.junit.jupiter.api.extension.ExtensionContext;
  * >  }
  * }</pre>
  */
-public class OpenTelemetryExtension
+public final class OpenTelemetryExtension
     implements BeforeEachCallback, BeforeAllCallback, AfterAllCallback {
 
   /**

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/SdkTracerProvider.java

@@ -26,7 +26,7 @@ import javax.annotation.Nullable;
  * OpenTelemetry}. However, if you need a custom implementation of the factory, you can create one
  * as needed.
  */
-public class SdkTracerProvider implements TracerProvider, SdkTracerManagement {
+public final class SdkTracerProvider implements TracerProvider, SdkTracerManagement {
   private static final Logger logger = Logger.getLogger(SdkTracerProvider.class.getName());
   static final String DEFAULT_TRACER_NAME = "unknown";
   private final TracerSharedState sharedState;

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/config/TraceConfigBuilder.java

@@ -15,7 +15,7 @@ import java.util.Map;
 import java.util.Properties;
 
 /** Builder for {@link TraceConfig}. */
-public class TraceConfigBuilder extends ConfigBuilder<TraceConfigBuilder> {
+public final class TraceConfigBuilder extends ConfigBuilder<TraceConfigBuilder> {
   private static final String KEY_SAMPLER_PROBABILITY = "otel.config.sampler.probability";
   private static final String KEY_SPAN_ATTRIBUTE_COUNT_LIMIT = "otel.span.attribute.count.limit";
   private static final String KEY_SPAN_EVENT_COUNT_LIMIT = "otel.span.event.count.limit";

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/samplers/ParentBasedSamplerBuilder.java

@@ -6,7 +6,7 @@
 package io.opentelemetry.sdk.trace.samplers;
 
 /** A builder for creating ParentBased sampler instances. */
-public class ParentBasedSamplerBuilder {
+public final class ParentBasedSamplerBuilder {
 
   private final Sampler root;
   private Sampler remoteParentSampled;