8361717: Refactor Collections.emptyList() in Locale related classes

Reviewed-by: bpb, jlu, liach, cstein

Author: naotoj

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

@@ -51,7 +51,7 @@ public record LanguageTag(String language, String script, String region, String
     public static final String UNDETERMINED = "und";
     public static final String PRIVUSE_VARIANT_PREFIX = "lvariant";
     private static final String EMPTY_SUBTAG = "";
-    private static final List<String> EMPTY_SUBTAGS = Collections.emptyList();
+    private static final List<String> EMPTY_SUBTAGS = List.of();
 
     // Map contains legacy language tags and its preferred mappings from
     // http://www.ietf.org/rfc/rfc5646.txt

src/java.base/share/classes/sun/util/locale/provider/LocaleServiceProviderPool.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -27,7 +27,6 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.IllformedLocaleException;
 import java.util.List;
@@ -388,8 +387,7 @@ static Locale getLookupLocale(Locale locale) {
      * A dummy locale service provider list that indicates there is no
      * provider available
      */
-    private static final List<LocaleServiceProvider> NULL_LIST =
-        Collections.emptyList();
+    private static final List<LocaleServiceProvider> NULL_LIST = List.of();
 
     /**
      * An interface to get a localized object for each locale sensitive