[Settings] Code refactor

Code refactor.

Bug: 146985715
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=AirplaneModePreferenceControllerTest
Change-Id: I3ecc85f0f4ae1a0164a88bf811fe4c865d517d03
diff --git a/src/com/android/settings/AirplaneModeEnabler.java b/src/com/android/settings/AirplaneModeEnabler.java
index 64ad17d..ee3eaa4 100644
--- a/src/com/android/settings/AirplaneModeEnabler.java
+++ b/src/com/android/settings/AirplaneModeEnabler.java
@@ -104,8 +104,8 @@
             }
         }
 
-        for (ServiceStateListener ssListener : mServiceStateListeners) {
-            ssListener.start();
+        for (ServiceStateListener listener : mServiceStateListeners) {
+            listener.start();
         }
     }
 
@@ -113,8 +113,8 @@
         if (mServiceStateListeners == null) {
             return;
         }
-        for (ServiceStateListener ssListener : mServiceStateListeners) {
-            ssListener.stop();
+        for (ServiceStateListener listener : mServiceStateListeners) {
+            listener.stop();
         }
         mServiceStateListeners = null;
     }
@@ -210,9 +210,9 @@
             mEnabler = enabler;
         }
 
-        private int mSubId;
-        private TelephonyManager mTelephonyManager;
-        private AirplaneModeEnabler mEnabler;
+        private final int mSubId;
+        private final TelephonyManager mTelephonyManager;
+        private final AirplaneModeEnabler mEnabler;
 
         int getSubscriptionId() {
             return mSubId;