8358426: Improve lazy computation in Locale

Reviewed-by: naoto, liach

src/java.base/share/classes/java/util/Locale.java

@@ -48,8 +48,8 @@ import java.io.Serializable;
 import java.text.NumberFormat;
 import java.text.MessageFormat;
 import java.text.ParsePosition;
-import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.spi.LocaleNameProvider;
 import java.util.stream.Stream;
 
@@ -733,58 +733,24 @@ public final class Locale implements Cloneable, Serializable {
      * @see #getISOCountries(Locale.IsoCountryCode)
      * @since 9
      */
-    public static enum IsoCountryCode {
+    public enum IsoCountryCode {
         /**
          * PART1_ALPHA2 is used to represent the ISO3166-1 alpha-2 two letter
          * country codes.
          */
-        PART1_ALPHA2 {
+        PART1_ALPHA2,
-            @Override
-            Set<String> createCountryCodeSet() {
-                return Set.of(Locale.getISOCountries());
-            }
-        },
 
         /**
          *
          * PART1_ALPHA3 is used to represent the ISO3166-1 alpha-3 three letter
          * country codes.
          */
-        PART1_ALPHA3 {
+        PART1_ALPHA3,
-            @Override
-            Set<String> createCountryCodeSet() {
-                return LocaleISOData.computeISO3166_1Alpha3Countries();
-            }
-        },
 
         /**
          * PART3 is used to represent the ISO3166-3 four letter country codes.
          */
-        PART3 {
+        PART3
-            @Override
-            Set<String> createCountryCodeSet() {
-                return Set.of(LocaleISOData.ISO3166_3);
-            }
-        };
-
-        /**
-         * Concrete implementation of this method attempts to compute value
-         * for iso3166CodesMap for each IsoCountryCode type key.
-         */
-        abstract Set<String> createCountryCodeSet();
-
-        /**
-         * Map to hold country codes for each ISO3166 part.
-         */
-        private static final Map<IsoCountryCode, Set<String>> iso3166CodesMap = new ConcurrentHashMap<>();
-
-        /**
-         * This method is called from Locale class to retrieve country code set
-         * for getISOCountries(type)
-         */
-        static Set<String> retrieveISOCountryCodes(IsoCountryCode type) {
-            return iso3166CodesMap.computeIfAbsent(type, IsoCountryCode::createCountryCodeSet);
-        }
     }
 
     /**
@@ -1004,30 +970,28 @@ public final class Locale implements Cloneable, Serializable {
         return getInstance(baseloc, extensions);
     }
 
-
     static Locale getInstance(BaseLocale baseloc, LocaleExtensions extensions) {
         if (extensions == null) {
             Locale locale = CONSTANT_LOCALES.get(baseloc);
             if (locale != null) {
                 return locale;
             }
-            return LocaleCache.cache(baseloc);
+            return LOCALE_CACHE.get().computeIfAbsent(baseloc, LOCALE_CREATOR);
         } else {
             LocaleKey key = new LocaleKey(baseloc, extensions);
-            return LocaleCache.cache(key);
+            return LOCALE_CACHE.get().computeIfAbsent(key, LOCALE_CREATOR);
         }
     }
 
-    private static final class LocaleCache implements Function<Object, Locale> {
+    private static final Supplier<ReferencedKeyMap<Object, Locale>> LOCALE_CACHE =
-        private static final ReferencedKeyMap<Object, Locale> LOCALE_CACHE
+            StableValue.supplier(new Supplier<>() {
-                = ReferencedKeyMap.create(true, ReferencedKeyMap.concurrentHashMapSupplier());
+                @Override
-
+                public ReferencedKeyMap<Object, Locale> get() {
-        private static final Function<Object, Locale> LOCALE_CREATOR = new LocaleCache();
+                    return ReferencedKeyMap.create(true, ReferencedKeyMap.concurrentHashMapSupplier());
-
+                }
-        public static Locale cache(Object key) {
+            });
-            return LOCALE_CACHE.computeIfAbsent(key, LOCALE_CREATOR);
-        }
 
+    private static final Function<Object, Locale> LOCALE_CREATOR = new Function<>() {
         @Override
         public Locale apply(Object key) {
             if (key instanceof BaseLocale base) {
@@ -1036,7 +1000,7 @@ public final class Locale implements Cloneable, Serializable {
             LocaleKey lk = (LocaleKey)key;
             return new Locale(lk.base, lk.exts);
         }
-    }
+    };
 
     private static final class LocaleKey {
 
@@ -1301,12 +1265,8 @@ public final class Locale implements Cloneable, Serializable {
      * @return An array of ISO 3166 two-letter country codes.
      */
     public static String[] getISOCountries() {
-        if (isoCountries == null) {
+        String[] countries = LocaleISOData.ISO_3166_1_ALPHA2.get();
-            isoCountries = getISO2Table(LocaleISOData.isoCountryTable);
+        return Arrays.copyOf(countries, countries.length);
-        }
-        String[] result = new String[isoCountries.length];
-        System.arraycopy(isoCountries, 0, result, 0, isoCountries.length);
-        return result;
     }
 
     /**
@@ -1319,7 +1279,11 @@ public final class Locale implements Cloneable, Serializable {
      */
     public static Set<String> getISOCountries(IsoCountryCode type) {
         Objects.requireNonNull(type);
-        return IsoCountryCode.retrieveISOCountryCodes(type);
+        return switch (type) {
+            case PART1_ALPHA2 -> Set.of(LocaleISOData.ISO_3166_1_ALPHA2.get());
+            case PART1_ALPHA3 -> LocaleISOData.ISO_3166_1_ALPHA3.get();
+            case PART3 -> LocaleISOData.ISO_3166_3.get();
+        };
     }
 
     /**
@@ -1339,22 +1303,8 @@ public final class Locale implements Cloneable, Serializable {
      * @return An array of ISO 639 two-letter language codes.
      */
     public static String[] getISOLanguages() {
-        String[] languages = Locale.isoLanguages;
+        String[] languages = LocaleISOData.ISO_639.get();
-        if (languages == null) {
+        return Arrays.copyOf(languages, languages.length);
-            Locale.isoLanguages = languages = getISO2Table(LocaleISOData.isoLanguageTable);
-        }
-        String[] result = new String[languages.length];
-        System.arraycopy(languages, 0, result, 0, languages.length);
-        return result;
-    }
-
-    private static String[] getISO2Table(String table) {
-        int len = table.length() / 5;
-        String[] isoTable = new String[len];
-        for (int i = 0, j = 0; i < len; i++, j += 5) {
-            isoTable[i] = table.substring(j, j + 2);
-        }
-        return isoTable;
     }
 
     /**
@@ -1683,61 +1633,54 @@ public final class Locale implements Cloneable, Serializable {
      * @since 1.7
      */
     public String toLanguageTag() {
-        String lTag = this.languageTag;
+        return languageTag.get();
-        if (lTag != null) {
+    }
-            return lTag;
-        }
 
+    private String computeLanguageTag() {
         LanguageTag tag = LanguageTag.parseLocale(baseLocale, localeExtensions);
-        StringBuilder buf = new StringBuilder();
+        StringBuilder bldr = new StringBuilder();
 
         String subtag = tag.language();
         if (!subtag.isEmpty()) {
-            buf.append(LanguageTag.canonicalizeLanguage(subtag));
+            bldr.append(LanguageTag.canonicalizeLanguage(subtag));
         }
 
         subtag = tag.script();
         if (!subtag.isEmpty()) {
-            buf.append(LanguageTag.SEP);
+            bldr.append(LanguageTag.SEP);
-            buf.append(LanguageTag.canonicalizeScript(subtag));
+            bldr.append(LanguageTag.canonicalizeScript(subtag));
         }
 
         subtag = tag.region();
         if (!subtag.isEmpty()) {
-            buf.append(LanguageTag.SEP);
+            bldr.append(LanguageTag.SEP);
-            buf.append(LanguageTag.canonicalizeRegion(subtag));
+            bldr.append(LanguageTag.canonicalizeRegion(subtag));
         }
 
         List<String>subtags = tag.variants();
         for (String s : subtags) {
-            buf.append(LanguageTag.SEP);
+            bldr.append(LanguageTag.SEP);
             // preserve casing
-            buf.append(s);
+            bldr.append(s);
         }
 
         subtags = tag.extensions();
         for (String s : subtags) {
-            buf.append(LanguageTag.SEP);
+            bldr.append(LanguageTag.SEP);
-            buf.append(LanguageTag.canonicalizeExtension(s));
+            bldr.append(LanguageTag.canonicalizeExtension(s));
         }
 
         subtag = tag.privateuse();
         if (!subtag.isEmpty()) {
-            if (buf.length() > 0) {
+            if (bldr.length() > 0) {
-                buf.append(LanguageTag.SEP);
+                bldr.append(LanguageTag.SEP);
             }
-            buf.append(LanguageTag.PRIVATEUSE).append(LanguageTag.SEP);
+            bldr.append(LanguageTag.PRIVATEUSE).append(LanguageTag.SEP);
             // preserve casing
-            buf.append(subtag);
+            bldr.append(subtag);
         }
 
-        String langTag = buf.toString();
+        return bldr.toString();
-        synchronized (this) {
-            if (this.languageTag == null) {
-                this.languageTag = langTag;
-            }
-        }
-        return langTag;
     }
 
     /**
@@ -1961,7 +1904,7 @@ public final class Locale implements Cloneable, Serializable {
             return lang;
         }
 
-        String language3 = getISO3Code(lang, LocaleISOData.isoLanguageTable);
+        String language3 = LocaleISOData.getISO3LangCode(lang);
         if (language3 == null) {
             throw new MissingResourceException("Couldn't find 3-letter language code for "
                     + lang, "FormatData_" + toString(), "ShortLanguage");
@@ -1983,7 +1926,7 @@ public final class Locale implements Cloneable, Serializable {
      * three-letter country abbreviation is not available for this locale.
      */
     public String getISO3Country() throws MissingResourceException {
-        String country3 = getISO3Code(baseLocale.getRegion(), LocaleISOData.isoCountryTable);
+        String country3 = LocaleISOData.getISO3CtryCode(baseLocale.getRegion());
         if (country3 == null) {
             throw new MissingResourceException("Couldn't find 3-letter country code for "
                     + baseLocale.getRegion(), "FormatData_" + toString(), "ShortCountry");
@@ -1991,27 +1934,6 @@ public final class Locale implements Cloneable, Serializable {
         return country3;
     }
 
-    private static String getISO3Code(String iso2Code, String table) {
-        int codeLength = iso2Code.length();
-        if (codeLength == 0) {
-            return "";
-        }
-
-        int tableLength = table.length();
-        int index = tableLength;
-        if (codeLength == 2) {
-            char c1 = iso2Code.charAt(0);
-            char c2 = iso2Code.charAt(1);
-            for (index = 0; index < tableLength; index += 5) {
-                if (table.charAt(index) == c1
-                    && table.charAt(index + 1) == c2) {
-                    break;
-                }
-            }
-        }
-        return index < tableLength ? table.substring(index + 2, index + 5) : null;
-    }
-
     /**
      * Returns a name for the locale's language that is appropriate for display to the
      * user.
@@ -2393,7 +2315,13 @@ public final class Locale implements Cloneable, Serializable {
     private static volatile Locale defaultDisplayLocale;
     private static volatile Locale defaultFormatLocale;
 
-    private transient volatile String languageTag;
+    private final transient Supplier<String> languageTag =
+            StableValue.supplier(new Supplier<>() {
+                @Override
+                public String get() {
+                    return computeLanguageTag();
+                }
+            });
 
     /**
      * Return an array of the display names of the variant.
@@ -2587,10 +2515,6 @@ public final class Locale implements Cloneable, Serializable {
                 baseLocale.getRegion(), baseLocale.getVariant(), localeExtensions);
     }
 
-    private static volatile String[] isoLanguages;
-
-    private static volatile String[] isoCountries;
-
     private static String convertOldISOCodes(String language) {
         // we accept both the old and the new ISO codes for the languages whose ISO
         // codes have changed, but we always store the NEW code, unless the property

src/java.base/share/classes/java/util/LocaleISOData.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
@@ -25,11 +25,47 @@
 
 package java.util;
 
+import java.util.function.Supplier;
+
+// Methods and suppliers for producing ISO 639/3166 resources used by Locale.
 class LocaleISOData {
+
+    static final Supplier<String[]> ISO_639 =
+            StableValue.supplier(new Supplier<>() {
+                @Override
+                public String[] get() {
+                    return getISO2Table(isoLanguageTable);
+                }
+            });
+
+    static final Supplier<String[]> ISO_3166_1_ALPHA2 =
+            StableValue.supplier(new Supplier<>() {
+                @Override
+                public String[] get() {
+                    return getISO2Table(isoCountryTable);
+                }
+            });
+
+    static final Supplier<Set<String>> ISO_3166_1_ALPHA3 =
+            StableValue.supplier(new Supplier<>() {
+                @Override
+                public Set<String> get() {
+                    return computeISO3166_1Alpha3Countries();
+                }
+            });
+
+    static final Supplier<Set<String>> ISO_3166_3 =
+            StableValue.supplier(new Supplier<>() {
+                @Override
+                public Set<String> get() {
+                    return Set.of(ISO3166_3);
+                }
+            });
+
     /**
      * The 2- and 3-letter ISO 639 language codes.
      */
-    static final String isoLanguageTable =
+    private static final String isoLanguageTable =
           "aa" + "aar"  // Afar
         + "ab" + "abk"  // Abkhazian
         + "ae" + "ave"  // Avestan
@@ -223,7 +259,7 @@ class LocaleISOData {
     /**
      * The 2- and 3-letter ISO 3166 country codes.
      */
-    static final String isoCountryTable =
+    private static final String isoCountryTable =
           "AD" + "AND"  // Andorra, Principality of
         + "AE" + "ARE"  // United Arab Emirates
         + "AF" + "AFG"  // Afghanistan
@@ -480,18 +516,60 @@ class LocaleISOData {
     /**
      * Array to hold country codes for ISO3166-3.
      */
-    static final String[] ISO3166_3 = {
+    private static final String[] ISO3166_3 = {
         "AIDJ", "ANHH", "BQAQ", "BUMM", "BYAA", "CSHH", "CSXX", "CTKI", "DDDE",
         "DYBJ", "FQHH", "FXFR", "GEHH", "HVBF", "JTUM", "MIUM", "NHVU", "NQAQ",
         "NTHH", "PCHH", "PUUM", "PZPA", "RHZW", "SKIN", "SUHH", "TPTL", "VDVN",
         "WKUM", "YDYE", "YUCS", "ZRCD"
     };
 
+    static String getISO3LangCode(String language) {
+        return getISO3Code(language, isoLanguageTable);
+    }
+
+    static String getISO3CtryCode(String country) {
+        return getISO3Code(country, isoCountryTable);
+    }
+
+    private static String getISO3Code(String iso2Code, String table) {
+        int codeLength = iso2Code.length();
+        if (codeLength == 0) {
+            return "";
+        }
+
+        int tableLength = table.length();
+        int index = tableLength;
+        if (codeLength == 2) {
+            char c1 = iso2Code.charAt(0);
+            char c2 = iso2Code.charAt(1);
+            for (index = 0; index < tableLength; index += 5) {
+                if (table.charAt(index) == c1
+                        && table.charAt(index + 1) == c2) {
+                    break;
+                }
+            }
+        }
+        return index < tableLength ? table.substring(index + 2, index + 5) : null;
+    }
+
+    /**
+     * This method computes an array of alpha-2 codes from either ISO639 or
+     * ISO3166.
+     */
+    private static String[] getISO2Table(String table) {
+        int len = table.length() / 5;
+        String[] isoTable = new String[len];
+        for (int i = 0, j = 0; i < len; i++, j += 5) {
+            isoTable[i] = table.substring(j, j + 2);
+        }
+        return isoTable;
+    }
+
     /**
      * This method computes a set of ISO3166-1 alpha-3 country codes from
      * existing isoCountryTable.
      */
-    static Set<String> computeISO3166_1Alpha3Countries() {
+    private static Set<String> computeISO3166_1Alpha3Countries() {
         int tableLength = isoCountryTable.length();
         String[] isoTable = new String[tableLength / 5];
         for (int i = 0, index = 0; index < tableLength; i++, index += 5) {
@@ -500,6 +578,5 @@ class LocaleISOData {
         return Set.of(isoTable);
     }
 
-    private LocaleISOData() {
+    private LocaleISOData() {}
-    }
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2010, 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
@@ -38,6 +38,7 @@ import jdk.internal.util.StaticProperty;
 import jdk.internal.vm.annotation.Stable;
 
 import java.util.StringJoiner;
+import java.util.function.Supplier;
 
 public final class BaseLocale {
 
@@ -90,6 +91,15 @@ public final class BaseLocale {
         }
     }
 
+    // Interned BaseLocale cache
+    private static final Supplier<ReferencedKeySet<BaseLocale>> CACHE =
+            StableValue.supplier(new Supplier<>() {
+                @Override
+                public ReferencedKeySet<BaseLocale> get() {
+                    return ReferencedKeySet.create(true, ReferencedKeySet.concurrentHashMapSupplier());
+                }
+            });
+
     public static final String SEP = "_";
 
     private final String language;
@@ -164,11 +174,7 @@ public final class BaseLocale {
         // Obtain the "interned" BaseLocale from the cache. The returned
         // "interned" instance can subsequently be used by the Locale
         // instance which guarantees the locale components are properly cased/interned.
-        class InterningCache { // TODO: StableValue
+        return CACHE.get().intern(new BaseLocale(
-            private static final ReferencedKeySet<BaseLocale> CACHE =
-                    ReferencedKeySet.create(true, ReferencedKeySet.concurrentHashMapSupplier());
-        }
-        return InterningCache.CACHE.intern(new BaseLocale(
                 language.intern(), // guaranteed to be lower-case
                 LocaleUtils.toTitleString(script).intern(),
                 region.intern(), // guaranteed to be upper-case