diff --git a/nfc/api/current.txt b/nfc/api/current.txt
index 447e980..5b6b6c0 100644
--- a/nfc/api/current.txt
+++ b/nfc/api/current.txt
@@ -220,14 +220,15 @@
     field @Deprecated public static final String ACTION_CHANGE_DEFAULT = "android.nfc.cardemulation.action.ACTION_CHANGE_DEFAULT";
     field public static final String CATEGORY_OTHER = "other";
     field public static final String CATEGORY_PAYMENT = "payment";
-    field @FlaggedApi("android.nfc.nfc_override_recover_routing_table") public static final String DH = "DH";
-    field @FlaggedApi("android.nfc.nfc_override_recover_routing_table") public static final String ESE = "ESE";
     field public static final String EXTRA_CATEGORY = "category";
     field public static final String EXTRA_SERVICE_COMPONENT = "component";
+    field @FlaggedApi("android.nfc.nfc_override_recover_routing_table") public static final int PROTOCOL_AND_TECHNOLOGY_ROUTE_DH = 0; // 0x0
+    field @FlaggedApi("android.nfc.nfc_override_recover_routing_table") public static final int PROTOCOL_AND_TECHNOLOGY_ROUTE_ESE = 1; // 0x1
+    field @FlaggedApi("android.nfc.nfc_override_recover_routing_table") public static final int PROTOCOL_AND_TECHNOLOGY_ROUTE_UICC = 2; // 0x2
+    field @FlaggedApi("android.nfc.nfc_override_recover_routing_table") public static final int PROTOCOL_AND_TECHNOLOGY_ROUTE_UNSET = -1; // 0xffffffff
     field public static final int SELECTION_MODE_ALWAYS_ASK = 1; // 0x1
     field public static final int SELECTION_MODE_ASK_IF_CONFLICT = 2; // 0x2
     field public static final int SELECTION_MODE_PREFER_DEFAULT = 0; // 0x0
-    field @FlaggedApi("android.nfc.nfc_override_recover_routing_table") public static final String UICC = "UICC";
   }
 
   public abstract class HostApduService extends android.app.Service {
diff --git a/nfc/api/system-current.txt b/nfc/api/system-current.txt
index 25a01b9..717e01e 100644
--- a/nfc/api/system-current.txt
+++ b/nfc/api/system-current.txt
@@ -94,7 +94,7 @@
   public final class CardEmulation {
     method @FlaggedApi("android.permission.flags.wallet_role_enabled") @Nullable @RequiresPermission(android.Manifest.permission.NFC_PREFERRED_PAYMENT_INFO) public static android.content.ComponentName getPreferredPaymentService(@NonNull android.content.Context);
     method @FlaggedApi("android.nfc.enable_nfc_mainline") @NonNull public java.util.List<android.nfc.cardemulation.ApduServiceInfo> getServices(@NonNull String, int);
-    method @FlaggedApi("android.nfc.nfc_override_recover_routing_table") public void overrideRoutingTable(@NonNull android.app.Activity, @Nullable String, @Nullable String);
+    method @FlaggedApi("android.nfc.nfc_override_recover_routing_table") public void overrideRoutingTable(@NonNull android.app.Activity, int, int);
     method @FlaggedApi("android.nfc.nfc_override_recover_routing_table") public void recoverRoutingTable(@NonNull android.app.Activity);
   }
 
diff --git a/nfc/java/android/nfc/cardemulation/CardEmulation.java b/nfc/java/android/nfc/cardemulation/CardEmulation.java
index 0605dbe..497309c 100644
--- a/nfc/java/android/nfc/cardemulation/CardEmulation.java
+++ b/nfc/java/android/nfc/cardemulation/CardEmulation.java
@@ -18,12 +18,12 @@
 
 import android.Manifest;
 import android.annotation.FlaggedApi;
+import android.annotation.IntDef;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
 import android.annotation.SdkConstant;
 import android.annotation.SdkConstant.SdkConstantType;
-import android.annotation.StringDef;
 import android.annotation.SystemApi;
 import android.annotation.UserHandleAware;
 import android.annotation.UserIdInt;
@@ -155,17 +155,23 @@
      * Route to Device Host (DH).
      */
     @FlaggedApi(Flags.FLAG_NFC_OVERRIDE_RECOVER_ROUTING_TABLE)
-    public static final String DH = "DH";
+    public static final int PROTOCOL_AND_TECHNOLOGY_ROUTE_DH = 0;
     /**
      * Route to eSE.
      */
     @FlaggedApi(Flags.FLAG_NFC_OVERRIDE_RECOVER_ROUTING_TABLE)
-    public static final String ESE = "ESE";
+    public static final int PROTOCOL_AND_TECHNOLOGY_ROUTE_ESE = 1;
     /**
      * Route to UICC.
      */
     @FlaggedApi(Flags.FLAG_NFC_OVERRIDE_RECOVER_ROUTING_TABLE)
-    public static final String UICC = "UICC";
+    public static final int PROTOCOL_AND_TECHNOLOGY_ROUTE_UICC = 2;
+
+    /**
+     * Route unset.
+     */
+    @FlaggedApi(Flags.FLAG_NFC_OVERRIDE_RECOVER_ROUTING_TABLE)
+    public static final int PROTOCOL_AND_TECHNOLOGY_ROUTE_UNSET = -1;
 
     static boolean sIsInitialized = false;
     static HashMap<Context, CardEmulation> sCardEmus = new HashMap<Context, CardEmulation>();
@@ -734,7 +740,7 @@
      *
      * @return the preferred payment service description
      */
-    @RequiresPermission(android.Manifest.permission.NFC_PREFERRED_PAYMENT_INFO)
+    @RequiresPermission(Manifest.permission.NFC_PREFERRED_PAYMENT_INFO)
     @Nullable
     public CharSequence getDescriptionForPreferredPaymentService() {
         ApduServiceInfo serviceInfo = callServiceReturn(() ->
@@ -884,10 +890,12 @@
     }
 
     /** @hide */
-    @StringDef({
-        DH,
-        ESE,
-        UICC
+    @IntDef(prefix = "PROTOCOL_AND_TECHNOLOGY_ROUTE_",
+            value = {
+                    PROTOCOL_AND_TECHNOLOGY_ROUTE_DH,
+                    PROTOCOL_AND_TECHNOLOGY_ROUTE_ESE,
+                    PROTOCOL_AND_TECHNOLOGY_ROUTE_UICC,
+                    PROTOCOL_AND_TECHNOLOGY_ROUTE_UNSET
     })
     @Retention(RetentionPolicy.SOURCE)
     public @interface ProtocolAndTechnologyRoute {}
@@ -896,29 +904,32 @@
       * Setting NFC controller routing table, which includes Protocol Route and Technology Route,
       * while this Activity is in the foreground.
       *
-      * The parameter set to null can be used to keep current values for that entry. Either
+      * The parameter set to {@link #PROTOCOL_AND_TECHNOLOGY_ROUTE_UNSET}
+      * can be used to keep current values for that entry. Either
       * Protocol Route or Technology Route should be override when calling this API, otherwise
       * throw {@link IllegalArgumentException}.
       * <p>
       * Example usage in an Activity that requires to set proto route to "ESE" and keep tech route:
       * <pre>
       * protected void onResume() {
-      *     mNfcAdapter.overrideRoutingTable(this , "ESE" , null);
+      *     mNfcAdapter.overrideRoutingTable(
+      *         this, {@link #PROTOCOL_AND_TECHNOLOGY_ROUTE_ESE}, null);
       * }</pre>
       * </p>
       * Also activities must call {@link #recoverRoutingTable(Activity)}
       * when it goes to the background. Only the package of the
       * currently preferred service (the service set as preferred by the current foreground
       * application via {@link CardEmulation#setPreferredService(Activity, ComponentName)} or the
-      * current Default Wallet Role Holder {@link android.app.role.RoleManager#ROLE_WALLET}),
+      * current Default Wallet Role Holder {@link RoleManager#ROLE_WALLET}),
       * otherwise a call to this method will fail and throw {@link SecurityException}.
       * @param activity The Activity that requests NFC controller routing table to be changed.
-      * @param protocol ISO-DEP route destination, which can be "DH" or "UICC" or "ESE".
-      * @param technology Tech-A, Tech-B and Tech-F route destination, which can be "DH" or "UICC"
-      * or "ESE".
+      * @param protocol ISO-DEP route destination, where the possible inputs are defined
+      *                 in {@link ProtocolAndTechnologyRoute}.
+      * @param technology Tech-A, Tech-B and Tech-F route destination, where the possible inputs
+      *                   are defined in {@link ProtocolAndTechnologyRoute}
       * @throws SecurityException if the caller is not the preferred NFC service
       * @throws IllegalArgumentException if the activity is not resumed or the caller is not in the
-      * foreground, or both protocol route and technology route are null.
+      * foreground.
       * <p>
       * This is a high risk API and only included to support mainline effort
       * @hide
@@ -926,25 +937,36 @@
     @SystemApi
     @FlaggedApi(Flags.FLAG_NFC_OVERRIDE_RECOVER_ROUTING_TABLE)
     public void overrideRoutingTable(
-            @NonNull Activity activity, @ProtocolAndTechnologyRoute @Nullable String protocol,
-            @ProtocolAndTechnologyRoute @Nullable String technology) {
+            @NonNull Activity activity, @ProtocolAndTechnologyRoute int protocol,
+            @ProtocolAndTechnologyRoute int technology) {
         if (!activity.isResumed()) {
             throw new IllegalArgumentException("Activity must be resumed.");
         }
-        if (protocol == null && technology == null) {
-            throw new IllegalArgumentException(("Both Protocol and Technology are null."));
-        }
+        String protocolRoute = switch (protocol) {
+            case PROTOCOL_AND_TECHNOLOGY_ROUTE_DH -> "DH";
+            case PROTOCOL_AND_TECHNOLOGY_ROUTE_ESE -> "ESE";
+            case PROTOCOL_AND_TECHNOLOGY_ROUTE_UICC -> "UICC";
+            case PROTOCOL_AND_TECHNOLOGY_ROUTE_UNSET -> null;
+            default -> throw new IllegalStateException("Unexpected value: " + protocol);
+        };
+        String technologyRoute = switch (technology) {
+            case PROTOCOL_AND_TECHNOLOGY_ROUTE_DH -> "DH";
+            case PROTOCOL_AND_TECHNOLOGY_ROUTE_ESE -> "ESE";
+            case PROTOCOL_AND_TECHNOLOGY_ROUTE_UICC -> "UICC";
+            case PROTOCOL_AND_TECHNOLOGY_ROUTE_UNSET -> null;
+            default -> throw new IllegalStateException("Unexpected value: " + protocol);
+        };
         callService(() ->
                 sService.overrideRoutingTable(
                     mContext.getUser().getIdentifier(),
-                    protocol,
-                    technology,
+                    protocolRoute,
+                    technologyRoute,
                     mContext.getPackageName()));
     }
 
     /**
      * Restore the NFC controller routing table,
-     * which was changed by {@link #overrideRoutingTable(Activity, String, String)}
+     * which was changed by {@link #overrideRoutingTable(Activity, int, int)}
      *
      * @param activity The Activity that requested NFC controller routing table to be changed.
      * @throws IllegalArgumentException if the caller is not in the foreground.