src/java.base/windows/classes/sun/util/locale/provider/HostLocaleProviderAdapterImpl.java

@@ -50,10 +50,11 @@
 import java.util.concurrent.atomic.AtomicReferenceArray;
 import java.util.spi.CalendarDataProvider;
 import java.util.spi.CalendarNameProvider;
 import java.util.spi.CurrencyNameProvider;
 import java.util.spi.LocaleNameProvider;
+import sun.text.spi.JavaTimeDateTimePatternProvider;
 import sun.util.spi.CalendarProvider;
 
 /**
  * LocaleProviderdapter implementation for the Windows locale data.
  *

@@ -523,10 +524,171 @@
                 return null;
             }
         };
     }
 
+    public static JavaTimeDateTimePatternProvider getJavaTimeDateTimePatternProvider() {
+        return new JavaTimeDateTimePatternProvider() {
+            @Override
+            public Locale[] getAvailableLocales() {
+                return getSupportedCalendarLocales();
+            }
+
+            @Override
+            public boolean isSupportedLocale(Locale locale) {
+                return isSupportedCalendarLocale(locale);
+            }
+
+            @Override
+            public String getJavaTimeDateTimePattern(int timeStyle, int dateStyle, String calType, Locale locale) {
+                AtomicReferenceArray<String> patterns = getDateTimePatterns(locale);
+                String pattern = new StringBuilder(patterns.get(dateStyle / 2))
+                        .append(" ")
+                        .append(patterns.get(timeStyle / 2 + 2))
+                        .toString();
+                return toJavaTimeDateTimePattern(calType, pattern);
+
+            }
+
+            private AtomicReferenceArray<String> getDateTimePatterns(Locale locale) {
+                AtomicReferenceArray<String> patterns;
+                SoftReference<AtomicReferenceArray<String>> ref = dateFormatCache.get(locale);
+
+                if (ref == null || (patterns = ref.get()) == null) {
+                    String langtag = removeExtensions(locale).toLanguageTag();
+                    patterns = new AtomicReferenceArray<>(4);
+                    patterns.compareAndSet(0, null, convertDateTimePattern(
+                            getDateTimePattern(DateFormat.LONG, -1, langtag)));
+                    patterns.compareAndSet(1, null, convertDateTimePattern(
+                            getDateTimePattern(DateFormat.SHORT, -1, langtag)));
+                    patterns.compareAndSet(2, null, convertDateTimePattern(
+                            getDateTimePattern(-1, DateFormat.LONG, langtag)));
+                    patterns.compareAndSet(3, null, convertDateTimePattern(
+                            getDateTimePattern(-1, DateFormat.SHORT, langtag)));
+                    ref = new SoftReference<>(patterns);
+                    dateFormatCache.put(locale, ref);
+                }
+                return patterns;
+            }
+            /**
+             * This method will convert JRE Date/time Pattern String to JSR310
+             * type Date/Time Pattern
+             */
+            private String toJavaTimeDateTimePattern(String calendarType, String jrePattern) {
+                int length = jrePattern.length();
+                StringBuilder sb = new StringBuilder();
+                boolean inQuote = false;
+                int count = 0;
+                char lastLetter = 0;
+                for (int i = 0; i < length; i++) {
+                    char c = jrePattern.charAt(i);
+                    if (c == '\'') {
+                        // '' is treated as a single quote regardless of being
+                        // in a quoted section.
+                        if ((i + 1) < length) {
+                            char nextc = jrePattern.charAt(i + 1);
+                            if (nextc == '\'') {
+                                i++;
+                                if (count != 0) {
+                                    convert(calendarType, lastLetter, count, sb);
+                                    lastLetter = 0;
+                                    count = 0;
+                                }
+                                sb.append("''");
+                                continue;
+                            }
+                        }
+                        if (!inQuote) {
+                            if (count != 0) {
+                                convert(calendarType, lastLetter, count, sb);
+                                lastLetter = 0;
+                                count = 0;
+                            }
+                            inQuote = true;
+                        } else {
+                            inQuote = false;
+                        }
+                        sb.append(c);
+                        continue;
+                    }
+                    if (inQuote) {
+                        sb.append(c);
+                        continue;
+                    }
+                    if (!(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z')) {
+                        if (count != 0) {
+                            convert(calendarType, lastLetter, count, sb);
+                            lastLetter = 0;
+                            count = 0;
+                        }
+                        sb.append(c);
+                        continue;
+                    }
+                    if (lastLetter == 0 || lastLetter == c) {
+                        lastLetter = c;
+                        count++;
+                        continue;
+                    }
+                    convert(calendarType, lastLetter, count, sb);
+                    lastLetter = c;
+                    count = 1;
+                }
+                if (inQuote) {
+                    // should not come here.
+                    // returning null so that FALLBACK provider will kick in.
+                    return null;
+                }
+                if (count != 0) {
+                    convert(calendarType, lastLetter, count, sb);
+                }
+                return sb.toString();
+            }
+
+            private void convert(String calendarType, char letter, int count, StringBuilder sb) {
+                switch (letter) {
+                    case 'G':
+                        if (calendarType.equals("japanese")) {
+                            if (count >= 4) {
+                                count = 1;
+                            } else {
+                                count = 5;
+                            }
+                        } else if (!calendarType.equals("iso8601")) {
+                            // Adjust the number of 'G's
+                            // Gregorian calendar is iso8601 for java.time
+                            if (count >= 4) {
+                                // JRE full -> JavaTime full
+                                count = 4;
+                            } else {
+                                // JRE short -> JavaTime short
+                                count = 1;
+                            }
+                        }
+                        break;
+                    case 'y':
+                        if (calendarType.equals("japanese") && count >= 4) {
+                            // JRE specific "gan-nen" support
+                            count = 1;
+                        }
+                        break;
+                    default:
+                        // JSR 310 and CLDR define 5-letter patterns for narrow text.
+                        if (count > 4) {
+                            count = 4;
+                        }
+                        break;
+                }
+                appendN(letter, count, sb);
+            }
+
+            private void appendN(char c, int n, StringBuilder sb) {
+                for (int i = 0; i < n; i++) {
+                    sb.append(c);
+                }
+            }
+        };
+    }
 
     private static String convertDateTimePattern(String winPattern) {
         String ret = winPattern.replaceAll("dddd", "EEEE");
         ret = ret.replaceAll("ddd", "EEE");
         ret = ret.replaceAll("tt", "aa");