Fixed potential string conversion issues

Replaced all toLowerCase() with toLowerCase(Locale.ROOT).
Replaced all toUpperCase() with toUpperCase(Locale.ROOT).

Fix: 250048156
Test: atest FrameworksTelephonyTests + Basic testing
Change-Id: I1dbfed792475377cd07bcf2b8265f2ae3a1117fc
diff --git a/src/com/android/phone/CallForwardEditPreference.java b/src/com/android/phone/CallForwardEditPreference.java
index 2cbb7c5..96915d4 100644
--- a/src/com/android/phone/CallForwardEditPreference.java
+++ b/src/com/android/phone/CallForwardEditPreference.java
@@ -28,6 +28,7 @@
 import com.android.internal.telephony.Phone;
 
 import java.util.HashMap;
+import java.util.Locale;
 
 public class CallForwardEditPreference extends EditPhoneNumberPreference {
     private static final String LOG_TAG = "CallForwardEditPreference";
@@ -287,7 +288,7 @@
         if (telephonyManager == null) {
             return "";
         }
-        return telephonyManager.getNetworkCountryIso().toUpperCase();
+        return telephonyManager.getNetworkCountryIso().toUpperCase(Locale.ROOT);
     }
 
     // Message protocol:
diff --git a/src/com/android/phone/TelephonyShellCommand.java b/src/com/android/phone/TelephonyShellCommand.java
index 11e5b69..463cdb1 100644
--- a/src/com/android/phone/TelephonyShellCommand.java
+++ b/src/com/android/phone/TelephonyShellCommand.java
@@ -1178,7 +1178,7 @@
             return 0;
         }
 
-        boolean isEnabled = "true".equals(arg.toLowerCase());
+        boolean isEnabled = "true".equals(arg.toLowerCase(Locale.ROOT));
         try {
             mInterface.setDeviceToDeviceForceEnabled(isEnabled);
         } catch (RemoteException e) {
diff --git a/src/com/android/phone/callcomposer/DigestAuthUtils.java b/src/com/android/phone/callcomposer/DigestAuthUtils.java
index 2f081f7..770aadf 100644
--- a/src/com/android/phone/callcomposer/DigestAuthUtils.java
+++ b/src/com/android/phone/callcomposer/DigestAuthUtils.java
@@ -30,6 +30,7 @@
 import java.security.NoSuchAlgorithmException;
 import java.security.SecureRandom;
 import java.text.ParseException;
+import java.util.Locale;
 
 public class DigestAuthUtils {
     private static final String TAG = DigestAuthUtils.class.getSimpleName();
@@ -54,12 +55,12 @@
     public static String generateAuthorizationHeader(WWWAuthenticate parsedHeader,
             GbaCredentials credentials, String method, String uri) {
         if (!TextUtils.isEmpty(parsedHeader.getAlgorithm())
-                && !MD5_ALGORITHM.equals(parsedHeader.getAlgorithm().toLowerCase())) {
+                && !MD5_ALGORITHM.equals(parsedHeader.getAlgorithm().toLowerCase(Locale.ROOT))) {
             Log.e(TAG, "This client only supports MD5 auth");
             return "";
         }
         if (!TextUtils.isEmpty(parsedHeader.getQop())
-                && !AUTH_QOP.equals(parsedHeader.getQop().toLowerCase())) {
+                && !AUTH_QOP.equals(parsedHeader.getQop().toLowerCase(Locale.ROOT))) {
             Log.e(TAG, "This client only supports the auth qop");
             return "";
         }
@@ -137,7 +138,7 @@
     }
 
     private static String base16(byte[] input) {
-        return BaseEncoding.base16().encode(input).toLowerCase();
+        return BaseEncoding.base16().encode(input).toLowerCase(Locale.ROOT);
     }
 
     private static MessageDigest getMd5Digest() {