diff --git a/api/current.txt b/api/current.txt
index 324a0b65843ff..f0393a28f5532 100755
--- a/api/current.txt
+++ b/api/current.txt
@@ -42959,7 +42959,7 @@ package android.telephony {
     method public String getCountryIso();
     method public int getDataRoaming();
     method public CharSequence getDisplayName();
-    method public String getGroupUuid();
+    method @Nullable public String getGroupUuid();
     method public String getIccId();
     method public int getIconTint();
     method @Deprecated public int getMcc();
@@ -43000,7 +43000,7 @@ package android.telephony {
     method public boolean isNetworkRoaming(int);
     method public static boolean isUsableSubscriptionId(int);
     method public static boolean isValidSubscriptionId(int);
-    method public void removeOnOpportunisticSubscriptionsChangedListener(android.telephony.SubscriptionManager.OnOpportunisticSubscriptionsChangedListener);
+    method public void removeOnOpportunisticSubscriptionsChangedListener(@NonNull android.telephony.SubscriptionManager.OnOpportunisticSubscriptionsChangedListener);
     method public void removeOnSubscriptionsChangedListener(android.telephony.SubscriptionManager.OnSubscriptionsChangedListener);
     method @RequiresPermission(android.Manifest.permission.MODIFY_PHONE_STATE) public boolean removeSubscriptionsFromGroup(@NonNull int[]);
     method @RequiresPermission(android.Manifest.permission.MODIFY_PHONE_STATE) public boolean setMetered(boolean, int);
@@ -43009,7 +43009,7 @@ package android.telephony {
     method public void setSubscriptionOverrideCongested(int, boolean, long);
     method public void setSubscriptionOverrideUnmetered(int, boolean, long);
     method public void setSubscriptionPlans(int, @NonNull java.util.List<android.telephony.SubscriptionPlan>);
-    method @RequiresPermission("android.permission.WRITE_EMBEDDED_SUBSCRIPTIONS") public void switchToSubscription(int, android.app.PendingIntent);
+    method @RequiresPermission("android.permission.WRITE_EMBEDDED_SUBSCRIPTIONS") public void switchToSubscription(int, @NonNull android.app.PendingIntent);
     field public static final String ACTION_DEFAULT_SMS_SUBSCRIPTION_CHANGED = "android.telephony.action.DEFAULT_SMS_SUBSCRIPTION_CHANGED";
     field public static final String ACTION_DEFAULT_SUBSCRIPTION_CHANGED = "android.telephony.action.DEFAULT_SUBSCRIPTION_CHANGED";
     field public static final String ACTION_MANAGE_SUBSCRIPTION_PLANS = "android.telephony.action.MANAGE_SUBSCRIPTION_PLANS";
diff --git a/telephony/java/android/telephony/SubscriptionInfo.java b/telephony/java/android/telephony/SubscriptionInfo.java
index 58f12e2c427af..b781b109bdcc9 100644
--- a/telephony/java/android/telephony/SubscriptionInfo.java
+++ b/telephony/java/android/telephony/SubscriptionInfo.java
@@ -467,7 +467,7 @@ public class SubscriptionInfo implements Parcelable {
      * @return group UUID a String of group UUID if it belongs to a group. Otherwise
      * it will return null.
      */
-    public String getGroupUuid() {
+    public @Nullable String getGroupUuid() {
         return mGroupUUID;
     }
 
diff --git a/telephony/java/android/telephony/SubscriptionManager.java b/telephony/java/android/telephony/SubscriptionManager.java
index 0bbf054d7563d..1377277bc8e2f 100644
--- a/telephony/java/android/telephony/SubscriptionManager.java
+++ b/telephony/java/android/telephony/SubscriptionManager.java
@@ -63,6 +63,7 @@ import com.android.internal.telephony.ISetOpportunisticDataCallback;
 import com.android.internal.telephony.ISub;
 import com.android.internal.telephony.ITelephonyRegistry;
 import com.android.internal.telephony.PhoneConstants;
+import com.android.internal.util.Preconditions;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -1075,7 +1076,8 @@ public class SubscriptionManager {
      * @param listener that is to be unregistered.
      */
     public void removeOnOpportunisticSubscriptionsChangedListener(
-            OnOpportunisticSubscriptionsChangedListener listener) {
+            @NonNull OnOpportunisticSubscriptionsChangedListener listener) {
+        Preconditions.checkNotNull(listener, "listener cannot be null");
         String pkgForDebug = mContext != null ? mContext.getOpPackageName() : "<unknown>";
         if (DBG) {
             logd("unregister OnOpportunisticSubscriptionsChangedListener pkgForDebug="
@@ -2699,7 +2701,8 @@ public class SubscriptionManager {
      *  @param callbackIntent pending intent that will be sent after operation is done.
      */
     @RequiresPermission(android.Manifest.permission.WRITE_EMBEDDED_SUBSCRIPTIONS)
-    public void switchToSubscription(int subId, PendingIntent callbackIntent) {
+    public void switchToSubscription(int subId, @NonNull PendingIntent callbackIntent) {
+        Preconditions.checkNotNull(callbackIntent, "callbackIntent cannot be null");
         EuiccManager euiccManager = new EuiccManager(mContext);
         euiccManager.switchToSubscription(subId, callbackIntent);
     }