src/java.base/share/classes/sun/util/locale/LocaleMatcher.java

@@ -116,11 +116,11 @@
             String range = lr.getRange();
             if (range.equals("*")) {
                 return new ArrayList<String>(tags);
             } else {
                 for (String tag : tags) {
-                    tag = tag.toLowerCase();
+                    tag = tag.toLowerCase(Locale.ROOT);
                     if (tag.startsWith(range)) {
                         int len = range.length();
                         if ((tag.length() == len || tag.charAt(len) == '-')
                             && !list.contains(tag)) {
                             list.add(tag);

@@ -141,11 +141,11 @@
             if (range.equals("*")) {
                 return new ArrayList<String>(tags);
             }
             String[] rangeSubtags = range.split("-");
             for (String tag : tags) {
-                tag = tag.toLowerCase();
+                tag = tag.toLowerCase(Locale.ROOT);
                 String[] tagSubtags = tag.split("-");
                 if (!rangeSubtags[0].equals(tagSubtags[0])
                     && !rangeSubtags[0].equals("*")) {
                     continue;
                 }

@@ -214,11 +214,11 @@
             }
 
             String rangeForRegex = range.replaceAll("\\x2A", "\\\\p{Alnum}*");
             while (rangeForRegex.length() > 0) {
                 for (String tag : tags) {
-                    tag = tag.toLowerCase();
+                    tag = tag.toLowerCase(Locale.ROOT);
                     if (tag.matches(rangeForRegex)) {
                         return tag;
                     }
                 }
 

@@ -241,11 +241,11 @@
 
         return null;
     }
 
     public static List<LanguageRange> parse(String ranges) {
-        ranges = ranges.replaceAll(" ", "").toLowerCase();
+        ranges = ranges.replaceAll(" ", "").toLowerCase(Locale.ROOT);
         if (ranges.startsWith("accept-language:")) {
             ranges = ranges.substring(16); // delete unnecessary prefix
         }
 
         String[] langRanges = ranges.split(",");

@@ -408,11 +408,11 @@
         }
 
         // Create a map, key=originalKey.toLowerCaes(), value=originalKey
         Map<String, String> keyMap = new HashMap<>();
         for (String key : map.keySet()) {
-            keyMap.put(key.toLowerCase(), key);
+            keyMap.put(key.toLowerCase(Locale.ROOT), key);
         }
 
         List<LanguageRange> list = new ArrayList<>();
         for (LanguageRange lr : priorityList) {
             String range = lr.getRange();

@@ -424,11 +424,11 @@
                     hasEquivalent = true;
                     List<String> equivalents = map.get(keyMap.get(r));
                     if (equivalents != null) {
                         int len = r.length();
                         for (String equivalent : equivalents) {
-                            list.add(new LanguageRange(equivalent.toLowerCase()
+                            list.add(new LanguageRange(equivalent.toLowerCase(Locale.ROOT)
                                      + range.substring(len),
                                      lr.getWeight()));
                         }
                     }
                     // Return immediately if the first matching subtag is found.