diff --git a/telecomm/java/android/telecom/Conference.java b/telecomm/java/android/telecom/Conference.java
index dc2fb94..f84dd7b 100644
--- a/telecomm/java/android/telecom/Conference.java
+++ b/telecomm/java/android/telecom/Conference.java
@@ -338,7 +338,7 @@
      *
      * @param videoState The video state in which to answer the connection.
      */
-    public void onAnswer(int videoState) {}
+    public void onAnswer(@VideoProfile.VideoState int videoState) {}
 
     /**
      * Notifies this Conference, which is in {@code STATE_RINGING}, of
diff --git a/telecomm/java/android/telecom/ConnectionService.java b/telecomm/java/android/telecom/ConnectionService.java
index b1ccb53..334bc08 100755
--- a/telecomm/java/android/telecom/ConnectionService.java
+++ b/telecomm/java/android/telecom/ConnectionService.java
@@ -2463,9 +2463,9 @@
      * @return The {@code Connection} object to satisfy this call, or {@code null} to
      *         not handle the call.
      */
-    public final RemoteConnection createRemoteIncomingConnection(
-            PhoneAccountHandle connectionManagerPhoneAccount,
-            ConnectionRequest request) {
+    public final @Nullable RemoteConnection createRemoteIncomingConnection(
+            @NonNull PhoneAccountHandle connectionManagerPhoneAccount,
+            @NonNull ConnectionRequest request) {
         return mRemoteConnectionManager.createRemoteConnection(
                 connectionManagerPhoneAccount, request, true);
     }
@@ -2482,9 +2482,9 @@
      * @return The {@code Connection} object to satisfy this call, or {@code null} to
      *         not handle the call.
      */
-    public final RemoteConnection createRemoteOutgoingConnection(
-            PhoneAccountHandle connectionManagerPhoneAccount,
-            ConnectionRequest request) {
+    public final @Nullable RemoteConnection createRemoteOutgoingConnection(
+            @NonNull PhoneAccountHandle connectionManagerPhoneAccount,
+            @NonNull ConnectionRequest request) {
         return mRemoteConnectionManager.createRemoteConnection(
                 connectionManagerPhoneAccount, request, false);
     }
@@ -2724,12 +2724,14 @@
      * @param connectionManagerPhoneAccount See description at
      *         {@link #onCreateOutgoingConnection(PhoneAccountHandle, ConnectionRequest)}.
      * @param request Details about the incoming conference call.
-     * @return The {@code Conference} object to satisfy this call, or {@code null} to
-     *         not handle the call.
+     * @return The {@code Conference} object to satisfy this call. If the conference attempt is
+     *         failed, the return value will be a result of an invocation of
+     *         {@link Connection#createFailedConnection(DisconnectCause)}.
+     *         Return {@code null} if the {@link ConnectionService} cannot handle the call.
      */
     public @Nullable Conference onCreateIncomingConference(
-            @Nullable PhoneAccountHandle connectionManagerPhoneAccount,
-            @Nullable ConnectionRequest request) {
+            @NonNull PhoneAccountHandle connectionManagerPhoneAccount,
+            @NonNull ConnectionRequest request) {
         return null;
     }
 
@@ -2832,8 +2834,8 @@
      * @param request The outgoing connection request.
      */
     public void onCreateOutgoingConferenceFailed(
-            @Nullable PhoneAccountHandle connectionManagerPhoneAccount,
-            @Nullable ConnectionRequest request) {
+            @NonNull PhoneAccountHandle connectionManagerPhoneAccount,
+            @NonNull ConnectionRequest request) {
     }
 
 
@@ -2897,12 +2899,14 @@
      *         a {@code PhoneAccount} registered by this {@code ConnectionService} to use for
      *         making the connection.
      * @param request Details about the outgoing call.
-     * @return The {@code Conference} object to satisfy this call, or the result of an invocation
-     *         of {@link Connection#createFailedConnection(DisconnectCause)} to not handle the call.
+     * @return The {@code Conference} object to satisfy this call. If the conference attempt is
+     *         failed, the return value will be a result of an invocation of
+     *         {@link Connection#createFailedConnection(DisconnectCause)}.
+     *         Return {@code null} if the {@link ConnectionService} cannot handle the call.
      */
     public @Nullable Conference onCreateOutgoingConference(
-            @Nullable PhoneAccountHandle connectionManagerPhoneAccount,
-            @Nullable ConnectionRequest request) {
+            @NonNull PhoneAccountHandle connectionManagerPhoneAccount,
+            @NonNull ConnectionRequest request) {
         return null;
     }