diff --git a/api/current.txt b/api/current.txt
index 7b05726..54814c7 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -38330,10 +38330,10 @@
     method public android.database.Cursor queryChildDocuments(String, @Nullable String[], @Nullable android.os.Bundle) throws java.io.FileNotFoundException;
     method public abstract android.database.Cursor queryDocument(String, String[]) throws java.io.FileNotFoundException;
     method public android.database.Cursor queryRecentDocuments(String, String[]) throws java.io.FileNotFoundException;
-    method public android.database.Cursor queryRecentDocuments(String, String[], @Nullable android.os.Bundle, @Nullable android.os.CancellationSignal) throws java.io.FileNotFoundException;
+    method @Nullable public android.database.Cursor queryRecentDocuments(@NonNull String, @Nullable String[], @Nullable android.os.Bundle, @Nullable android.os.CancellationSignal) throws java.io.FileNotFoundException;
     method public abstract android.database.Cursor queryRoots(String[]) throws java.io.FileNotFoundException;
     method public android.database.Cursor querySearchDocuments(String, String, String[]) throws java.io.FileNotFoundException;
-    method public android.database.Cursor querySearchDocuments(@NonNull String, @Nullable String[], @NonNull android.os.Bundle) throws java.io.FileNotFoundException;
+    method @Nullable public android.database.Cursor querySearchDocuments(@NonNull String, @Nullable String[], @NonNull android.os.Bundle) throws java.io.FileNotFoundException;
     method public void removeDocument(String, String) throws java.io.FileNotFoundException;
     method public String renameDocument(String, String) throws java.io.FileNotFoundException;
     method public final void revokeDocumentPermission(String);
diff --git a/api/system-current.txt b/api/system-current.txt
index 98464d8..b831785 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -5929,8 +5929,8 @@
   }
 
   public final class DocumentsContract {
-    method public static boolean isManageMode(android.net.Uri);
-    method public static android.net.Uri setManageMode(android.net.Uri);
+    method public static boolean isManageMode(@NonNull android.net.Uri);
+    method @NonNull public static android.net.Uri setManageMode(@NonNull android.net.Uri);
     field public static final String ACTION_DOCUMENT_ROOT_SETTINGS = "android.provider.action.DOCUMENT_ROOT_SETTINGS";
     field public static final String ACTION_MANAGE_DOCUMENT = "android.provider.action.MANAGE_DOCUMENT";
     field public static final String EXTRA_SHOW_ADVANCED = "android.provider.extra.SHOW_ADVANCED";
diff --git a/core/java/android/provider/DocumentsContract.java b/core/java/android/provider/DocumentsContract.java
index 49567b2..4632b75 100644
--- a/core/java/android/provider/DocumentsContract.java
+++ b/core/java/android/provider/DocumentsContract.java
@@ -1252,7 +1252,8 @@
      * {@hide}
      */
     @SystemApi
-    public static Uri setManageMode(Uri uri) {
+    public static @NonNull Uri setManageMode(@NonNull Uri uri) {
+        Preconditions.checkNotNull(uri, "uri can not be null");
         return uri.buildUpon().appendQueryParameter(PARAM_MANAGE, "true").build();
     }
 
@@ -1262,7 +1263,8 @@
      * {@hide}
      */
     @SystemApi
-    public static boolean isManageMode(Uri uri) {
+    public static boolean isManageMode(@NonNull Uri uri) {
+        Preconditions.checkNotNull(uri, "uri can not be null");
         return uri.getBooleanQueryParameter(PARAM_MANAGE, false);
     }
 
diff --git a/core/java/android/provider/DocumentsProvider.java b/core/java/android/provider/DocumentsProvider.java
index 9b9e2de..cb794ad 100644
--- a/core/java/android/provider/DocumentsProvider.java
+++ b/core/java/android/provider/DocumentsProvider.java
@@ -487,10 +487,12 @@
      * @see DocumentsContract#EXTRA_LOADING
      */
     @SuppressWarnings("unused")
+    @Nullable
     public Cursor queryRecentDocuments(
-            String rootId, String[] projection, @Nullable Bundle queryArgs,
-            @Nullable CancellationSignal signal)
-            throws FileNotFoundException {
+            @NonNull String rootId, @Nullable String[] projection, @Nullable Bundle queryArgs,
+            @Nullable CancellationSignal signal) throws FileNotFoundException {
+        Preconditions.checkNotNull(rootId, "rootId can not be null");
+
         Cursor c = queryRecentDocuments(rootId, projection);
         Bundle extras = new Bundle();
         c.setExtras(extras);
@@ -697,8 +699,9 @@
      * @see DocumentsContract#EXTRA_ERROR
      */
     @SuppressWarnings("unused")
-    public Cursor querySearchDocuments(@NonNull String rootId, @Nullable String[] projection,
-            @NonNull Bundle queryArgs) throws FileNotFoundException {
+    @Nullable
+    public Cursor querySearchDocuments(@NonNull String rootId,
+            @Nullable String[] projection, @NonNull Bundle queryArgs) throws FileNotFoundException {
         Preconditions.checkNotNull(rootId, "rootId can not be null");
         Preconditions.checkNotNull(queryArgs, "queryArgs can not be null");
         return querySearchDocuments(rootId, DocumentsContract.getSearchDocumentsQuery(queryArgs),