ICU-23199 Using 'C' in skeleton throws for some locales

Author: mihnita

icu4c/source/test/intltest/dtptngts.cpp

@@ -1159,7 +1159,8 @@ void IntlTestDateTimePatternGeneratorAPI::testC() {
             {"en",     "CCCCCCm", "hh:mm\\u202Faaaaa"},
             {"en-BN",  "Cm",      "h:mm\\u202Fb"},
             {"gu-IN",  "Cm",      "h:mm B"},
-            {"und-IN", "Cm",      "h:mm B"}
+            {"und-IN", "Cm",      "h:mm B"},
+            {"fi",     "Cm",      "H.mm"}
     };
 
     UErrorCode status = U_ZERO_ERROR;

icu4j/main/core/src/main/java/com/ibm/icu/text/DateTimePatternGenerator.java

@@ -423,7 +423,11 @@ private void getAllowedHourFormats(ULocale uLocale) {
 
         if (list != null) {
             defaultHourFormatChar = defaultCharFromLocale != null ? defaultCharFromLocale : list[0].charAt(0);
-            allowedHourFormats = Arrays.copyOfRange(list, 1, list.length - 1);
+            if (list.length > 1) {
+                allowedHourFormats = Arrays.copyOfRange(list, 1, list.length);
+            } else {
+                allowedHourFormats = LAST_RESORT_ALLOWED_HOUR_FORMAT;
+            }
         } else {
             allowedHourFormats = LAST_RESORT_ALLOWED_HOUR_FORMAT;
             defaultHourFormatChar = (defaultCharFromLocale != null) ? defaultCharFromLocale : allowedHourFormats[0].charAt(0);

icu4j/main/core/src/test/java/com/ibm/icu/dev/test/format/DateTimeGeneratorTest.java

@@ -77,6 +77,7 @@ public void TestC() {
                 {"en-BN",  "Cm",      "h:mm\u202Fb"},
                 {"gu-IN",  "Cm",      "h:mm B"},
                 {"und-IN", "Cm",      "h:mm B"},
+                {"fi",     "Cm",      "H.mm"},
         };
         for (String[] test : tests) {
             DateTimePatternGenerator gen = DateTimePatternGenerator.getInstance(ULocale.forLanguageTag(test[0]));