diff --git a/common/src/com/android/inputmethod/latin/common/LocaleUtils.java b/common/src/com/android/inputmethod/latin/common/LocaleUtils.java
index 14b3d22..7f2333b 100644
--- a/common/src/com/android/inputmethod/latin/common/LocaleUtils.java
+++ b/common/src/com/android/inputmethod/latin/common/LocaleUtils.java
@@ -17,8 +17,12 @@
 package com.android.inputmethod.latin.common;
 
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Locale;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * A class to help with handling Locales in string form.
  *
@@ -160,26 +164,49 @@
 
     /**
      * Creates a locale from a string specification.
+     * @param localeString a string specification of a locale, in a format of "ll_cc_variant" where
+     * "ll" is a language code, "cc" is a country code.
      */
-    public static Locale constructLocaleFromString(final String localeStr) {
-        if (localeStr == null)
+    @Nullable
+    public static Locale constructLocaleFromString(@Nullable final String localeString) {
+        if (localeString == null) {
             return null;
-        synchronized (sLocaleCache) {
-            if (sLocaleCache.containsKey(localeStr))
-                return sLocaleCache.get(localeStr);
-            Locale retval = null;
-            String[] localeParams = localeStr.split("_", 3);
-            if (localeParams.length == 1) {
-                retval = new Locale(localeParams[0]);
-            } else if (localeParams.length == 2) {
-                retval = new Locale(localeParams[0], localeParams[1]);
-            } else if (localeParams.length == 3) {
-                retval = new Locale(localeParams[0], localeParams[1], localeParams[2]);
-            }
-            if (retval != null) {
-                sLocaleCache.put(localeStr, retval);
-            }
-            return retval;
         }
+        synchronized (sLocaleCache) {
+            if (sLocaleCache.containsKey(localeString)) {
+                return sLocaleCache.get(localeString);
+            }
+            final String[] elements = localeString.split("_", 3);
+            final Locale locale;
+            if (elements.length == 1) {
+                locale = new Locale(elements[0] /* language */);
+            } else if (elements.length == 2) {
+                locale = new Locale(elements[0] /* language */, elements[1] /* country */);
+            } else { // localeParams.length == 3
+                locale = new Locale(elements[0] /* language */, elements[1] /* country */,
+                        elements[2] /* variant */);
+            }
+            sLocaleCache.put(localeString, locale);
+            return locale;
+        }
+    }
+
+    // TODO: Get this information from the framework instead of maintaining here by ourselves.
+    private static final HashSet<String> sRtlLanguageCodes = new HashSet<>();
+    static {
+        // List of known Right-To-Left language codes.
+        sRtlLanguageCodes.add("ar"); // Arabic
+        sRtlLanguageCodes.add("fa"); // Persian
+        sRtlLanguageCodes.add("iw"); // Hebrew
+        sRtlLanguageCodes.add("ku"); // Kurdish
+        sRtlLanguageCodes.add("ps"); // Pashto
+        sRtlLanguageCodes.add("sd"); // Sindhi
+        sRtlLanguageCodes.add("ug"); // Uyghur
+        sRtlLanguageCodes.add("ur"); // Urdu
+        sRtlLanguageCodes.add("yi"); // Yiddish
+    }
+
+    public static boolean isRtlLanguage(@Nonnull final Locale locale) {
+        return sRtlLanguageCodes.contains(locale.getLanguage());
     }
 }
diff --git a/java/src/com/android/inputmethod/keyboard/internal/KeyboardBuilder.java b/java/src/com/android/inputmethod/keyboard/internal/KeyboardBuilder.java
index 56c57b0..51f89c1 100644
--- a/java/src/com/android/inputmethod/keyboard/internal/KeyboardBuilder.java
+++ b/java/src/com/android/inputmethod/keyboard/internal/KeyboardBuilder.java
@@ -36,7 +36,6 @@
 import com.android.inputmethod.latin.common.Constants;
 import com.android.inputmethod.latin.common.StringUtils;
 import com.android.inputmethod.latin.utils.ResourceUtils;
-import com.android.inputmethod.latin.utils.SubtypeLocaleUtils;
 import com.android.inputmethod.latin.utils.XmlParseUtils;
 import com.android.inputmethod.latin.utils.XmlParseUtils.ParseException;
 
diff --git a/java/src/com/android/inputmethod/latin/RichInputMethodSubtype.java b/java/src/com/android/inputmethod/latin/RichInputMethodSubtype.java
index 2bcb274..ea8d4a2 100644
--- a/java/src/com/android/inputmethod/latin/RichInputMethodSubtype.java
+++ b/java/src/com/android/inputmethod/latin/RichInputMethodSubtype.java
@@ -135,7 +135,7 @@
 
     public boolean isRtlSubtype() {
         // The subtype is considered RTL if the language of the main subtype is RTL.
-        return SubtypeLocaleUtils.isRtlLanguage(mLocales[0]);
+        return LocaleUtils.isRtlLanguage(mLocales[0]);
     }
 
     // TODO: remove this method
diff --git a/java/src/com/android/inputmethod/latin/suggestions/SuggestionStripLayoutHelper.java b/java/src/com/android/inputmethod/latin/suggestions/SuggestionStripLayoutHelper.java
index 27a0f62..7991a24 100644
--- a/java/src/com/android/inputmethod/latin/suggestions/SuggestionStripLayoutHelper.java
+++ b/java/src/com/android/inputmethod/latin/suggestions/SuggestionStripLayoutHelper.java
@@ -50,10 +50,10 @@
 import com.android.inputmethod.latin.R;
 import com.android.inputmethod.latin.SuggestedWords;
 import com.android.inputmethod.latin.SuggestedWords.SuggestedWordInfo;
+import com.android.inputmethod.latin.common.LocaleUtils;
 import com.android.inputmethod.latin.settings.Settings;
 import com.android.inputmethod.latin.settings.SettingsValues;
 import com.android.inputmethod.latin.utils.ResourceUtils;
-import com.android.inputmethod.latin.utils.SubtypeLocaleUtils;
 import com.android.inputmethod.latin.utils.ViewLayoutUtils;
 
 import java.util.ArrayList;
@@ -570,8 +570,7 @@
             final boolean isRtlLanguage = (ViewCompat.getLayoutDirection(addToDictionaryStrip)
                     == ViewCompat.LAYOUT_DIRECTION_RTL);
             final String arrow = isRtlLanguage ? RIGHTWARDS_ARROW : LEFTWARDS_ARROW;
-            final boolean isRtlSystem = SubtypeLocaleUtils.isRtlLanguage(
-                    res.getConfiguration().locale);
+            final boolean isRtlSystem = LocaleUtils.isRtlLanguage(res.getConfiguration().locale);
             final CharSequence hint = res.getText(R.string.hint_add_to_dictionary);
             hintText = (isRtlLanguage == isRtlSystem) ? (arrow + hint) : (hint + arrow);
             hintWidth = width - wordWidth;
diff --git a/java/src/com/android/inputmethod/latin/utils/SubtypeLocaleUtils.java b/java/src/com/android/inputmethod/latin/utils/SubtypeLocaleUtils.java
index af9c4ba..013f024 100644
--- a/java/src/com/android/inputmethod/latin/utils/SubtypeLocaleUtils.java
+++ b/java/src/com/android/inputmethod/latin/utils/SubtypeLocaleUtils.java
@@ -27,11 +27,9 @@
 import android.view.inputmethod.InputMethodSubtype;
 
 import com.android.inputmethod.latin.R;
-import com.android.inputmethod.latin.RichInputMethodSubtype;
 import com.android.inputmethod.latin.common.LocaleUtils;
 import com.android.inputmethod.latin.common.StringUtils;
 
-import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Locale;
 
@@ -347,22 +345,6 @@
         return keyboardLayoutSet;
     }
 
-    // TODO: Get this information from the framework instead of maintaining here by ourselves.
-    // Sorted list of known Right-To-Left language codes.
-    private static final String[] SORTED_RTL_LANGUAGES = {
-        "ar", // Arabic
-        "fa", // Persian
-        "iw", // Hebrew
-    };
-    static {
-        Arrays.sort(SORTED_RTL_LANGUAGES);
-    }
-
-    public static boolean isRtlLanguage(final Locale locale) {
-        final String language = locale.getLanguage();
-        return Arrays.binarySearch(SORTED_RTL_LANGUAGES, language) >= 0;
-    }
-
     public static String getCombiningRulesExtraValue(final InputMethodSubtype subtype) {
         return subtype.getExtraValueOf(COMBINING_RULES);
     }