diff --git a/android-interop-testing/src/main/java/io/grpc/android/integrationtest/InteropTask.java b/android-interop-testing/src/main/java/io/grpc/android/integrationtest/InteropTask.java
index caeafb723d9f..6ff34c5e54c4 100644
--- a/android-interop-testing/src/main/java/io/grpc/android/integrationtest/InteropTask.java
+++ b/android-interop-testing/src/main/java/io/grpc/android/integrationtest/InteropTask.java
@@ -64,7 +64,6 @@ protected String doInBackground(Void... ignored) {
       // Then print to the error message.
       StringWriter sw = new StringWriter();
       t.printStackTrace(new PrintWriter(sw));
-      return "Failed... : " + t.getMessage() + "\n" + sw;
     } finally {
       try {
         tester.tearDown();
@@ -145,7 +144,6 @@ protected void onPostExecute(String result) {
   }
 
   private static class Tester extends AbstractInteropTest {
-    private final ManagedChannel channel;
 
     private Tester(ManagedChannel channel) {
       this.channel = channel;
diff --git a/android-interop-testing/src/main/java/io/grpc/android/integrationtest/TesterActivity.java b/android-interop-testing/src/main/java/io/grpc/android/integrationtest/TesterActivity.java
index 4081439f2396..004950e73804 100644
--- a/android-interop-testing/src/main/java/io/grpc/android/integrationtest/TesterActivity.java
+++ b/android-interop-testing/src/main/java/io/grpc/android/integrationtest/TesterActivity.java
@@ -31,7 +31,7 @@
 import com.google.android.gms.security.ProviderInstaller;
 import io.grpc.ManagedChannel;
 import java.io.InputStream;
-import java.util.LinkedList;
+import java.util.ArrayList;
 import java.util.List;
 
 public class TesterActivity extends AppCompatActivity
@@ -48,7 +48,7 @@ public class TesterActivity extends AppCompatActivity
   protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.activity_tester);
-    buttons = new LinkedList<>();
+    buttons = new ArrayList<>();
     buttons.add((Button) findViewById(R.id.empty_unary_button));
     buttons.add((Button) findViewById(R.id.large_unary_button));
     buttons.add((Button) findViewById(R.id.client_streaming_button));