diff --git a/benchmarks/src/main/java/io/grpc/benchmarks/qps/AbstractConfigurationBuilder.java b/benchmarks/src/main/java/io/grpc/benchmarks/qps/AbstractConfigurationBuilder.java
index 378c1609af..59624a4cea 100644
--- a/benchmarks/src/main/java/io/grpc/benchmarks/qps/AbstractConfigurationBuilder.java
+++ b/benchmarks/src/main/java/io/grpc/benchmarks/qps/AbstractConfigurationBuilder.java
@@ -23,6 +23,7 @@ import com.google.common.base.Strings;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeMap;
@@ -204,7 +205,7 @@ public abstract class AbstractConfigurationBuilder<T extends Configuration>
   }
 
   private static String commandLineFlag(Param param) {
-    String name = param.getName().toLowerCase();
+    String name = param.getName().toLowerCase(Locale.ROOT);
     String type = (!param.getType().isEmpty() ? '=' + param.getType() : "");
     return "--" + name + type;
   }
diff --git a/core/src/main/java/io/grpc/internal/AutoConfiguredLoadBalancerFactory.java b/core/src/main/java/io/grpc/internal/AutoConfiguredLoadBalancerFactory.java
index 6c476557d1..1e41dee497 100644
--- a/core/src/main/java/io/grpc/internal/AutoConfiguredLoadBalancerFactory.java
+++ b/core/src/main/java/io/grpc/internal/AutoConfiguredLoadBalancerFactory.java
@@ -189,7 +189,7 @@ public final class AutoConfiguredLoadBalancerFactory extends LoadBalancer.Factor
         throws PolicyException {
       // Check for balancer addresses
       boolean haveBalancerAddress = false;
-      List<EquivalentAddressGroup> backendAddrs = new ArrayList<EquivalentAddressGroup>();
+      List<EquivalentAddressGroup> backendAddrs = new ArrayList<>();
       for (EquivalentAddressGroup s : servers) {
         if (s.getAttributes().get(GrpcAttributes.ATTR_LB_ADDR_AUTHORITY) != null) {
           haveBalancerAddress = true;
diff --git a/core/src/main/java/io/grpc/internal/ServiceConfigUtil.java b/core/src/main/java/io/grpc/internal/ServiceConfigUtil.java
index 31312a45a8..4fd773f3cc 100644
--- a/core/src/main/java/io/grpc/internal/ServiceConfigUtil.java
+++ b/core/src/main/java/io/grpc/internal/ServiceConfigUtil.java
@@ -26,6 +26,7 @@ import java.text.ParseException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 import javax.annotation.Nullable;
@@ -320,7 +321,7 @@ public final class ServiceConfigUtil {
       "loadBalancingPolicy": "ROUND_ROBIN"  // The deprecated policy key
     }
     */
-    List<Map<String, Object>> lbConfigs = new ArrayList<Map<String, Object>>();
+    List<Map<String, Object>> lbConfigs = new ArrayList<>();
     if (serviceConfig.containsKey(SERVICE_CONFIG_LOAD_BALANCING_CONFIG_KEY)) {
       List<Object> configs = getList(serviceConfig, SERVICE_CONFIG_LOAD_BALANCING_CONFIG_KEY);
       for (Object config : configs) {
@@ -332,7 +333,7 @@ public final class ServiceConfigUtil {
       if (serviceConfig.containsKey(SERVICE_CONFIG_LOAD_BALANCING_POLICY_KEY)) {
         String policy = getString(serviceConfig, SERVICE_CONFIG_LOAD_BALANCING_POLICY_KEY);
         // Convert the policy to a config, so that the caller can handle them in the same way.
-        policy = policy.toLowerCase();
+        policy = policy.toLowerCase(Locale.ROOT);
         Map<String, Object> fakeConfig =
             Collections.singletonMap(policy, (Object) Collections.emptyMap());
         lbConfigs.add(fakeConfig);
diff --git a/core/src/test/java/io/grpc/internal/AutoConfiguredLoadBalancerFactoryTest.java b/core/src/test/java/io/grpc/internal/AutoConfiguredLoadBalancerFactoryTest.java
index a74a7fef4c..a7f9bd453a 100644
--- a/core/src/test/java/io/grpc/internal/AutoConfiguredLoadBalancerFactoryTest.java
+++ b/core/src/test/java/io/grpc/internal/AutoConfiguredLoadBalancerFactoryTest.java
@@ -399,7 +399,7 @@ public class AutoConfiguredLoadBalancerFactoryTest {
 
     assertThat(selection.provider).isInstanceOf(FakeRoundRobinLoadBalancerProvider.class);
     // Balancer addresses are filtered out in the server list passed to round_robin
-    assertThat(selection.serverList).isEqualTo(Collections.singletonList(servers.get(1)));
+    assertThat(selection.serverList).containsExactly(servers.get(1));
     assertThat(selection.config).isNull();
     verifyNoMoreInteractions(channelLogger);
   }
@@ -424,7 +424,8 @@ public class AutoConfiguredLoadBalancerFactoryTest {
       lb.decideLoadBalancerProvider(servers, serviceConfig);
       fail("Should throw");
     } catch (PolicyException e) {
-      assertThat(e.getMessage())
+      assertThat(e)
+          .hasMessageThat()
           .isEqualTo("Received ONLY balancer addresses but grpclb runtime is missing");
     }
   }
@@ -433,7 +434,7 @@ public class AutoConfiguredLoadBalancerFactoryTest {
   public void decideLoadBalancerProvider_serviceConfigLbPolicyOverridesDefault() throws Exception {
     AutoConfiguredLoadBalancer lb =
         (AutoConfiguredLoadBalancer) lbf.newLoadBalancer(new TestHelper());
-    Map<String, Object> serviceConfig = new HashMap<String, Object>();
+    Map<String, Object> serviceConfig = new HashMap<>();
     serviceConfig.put("loadBalancingPolicy", "round_robin");
     List<EquivalentAddressGroup> servers =
         Collections.singletonList(new EquivalentAddressGroup(new SocketAddress(){}));
@@ -466,7 +467,7 @@ public class AutoConfiguredLoadBalancerFactoryTest {
   public void decideLoadBalancerProvider_serviceConfigLbPolicyFailsOnUnknown() {
     AutoConfiguredLoadBalancer lb =
         (AutoConfiguredLoadBalancer) lbf.newLoadBalancer(new TestHelper());
-    Map<String, Object> serviceConfig = new HashMap<String, Object>();
+    Map<String, Object> serviceConfig = new HashMap<>();
     serviceConfig.put("loadBalancingPolicy", "MAGIC_BALANCER");
     List<EquivalentAddressGroup> servers =
         Collections.singletonList(new EquivalentAddressGroup(new SocketAddress(){}));
@@ -474,7 +475,7 @@ public class AutoConfiguredLoadBalancerFactoryTest {
       lb.decideLoadBalancerProvider(servers, serviceConfig);
       fail();
     } catch (PolicyException e) {
-      assertThat(e.getMessage()).isEqualTo(
+      assertThat(e).hasMessageThat().isEqualTo(
           "None of [magic_balancer] specified by Service Config are available.");
     }
   }
@@ -491,7 +492,7 @@ public class AutoConfiguredLoadBalancerFactoryTest {
       lb.decideLoadBalancerProvider(servers, serviceConfig);
       fail();
     } catch (PolicyException e) {
-      assertThat(e.getMessage()).isEqualTo(
+      assertThat(e).hasMessageThat().isEqualTo(
           "None of [magic_balancer] specified by Service Config are available.");
     }
   }
diff --git a/interop-testing/src/main/java/io/grpc/testing/integration/Http2Client.java b/interop-testing/src/main/java/io/grpc/testing/integration/Http2Client.java
index 7a579e59b1..d5423c9071 100644
--- a/interop-testing/src/main/java/io/grpc/testing/integration/Http2Client.java
+++ b/interop-testing/src/main/java/io/grpc/testing/integration/Http2Client.java
@@ -37,6 +37,7 @@ import java.net.InetSocketAddress;
 import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
@@ -368,7 +369,7 @@ public final class Http2Client {
   private static String validTestCasesHelpText() {
     StringBuilder builder = new StringBuilder();
     for (Http2TestCases testCase : Http2TestCases.values()) {
-      String strTestcase = testCase.name().toLowerCase();
+      String strTestcase = testCase.name().toLowerCase(Locale.ROOT);
       builder.append("\n      ")
           .append(strTestcase)
           .append(": ")