From d2571ea76ae5a9ccb7053bfec24bf3aedd366084 Mon Sep 17 00:00:00 2001
From: Naoto Sato <naoto@openjdk.org>
Date: Thu, 13 Nov 2025 00:31:10 +0000
Subject: [PATCH] 8371339: Illegal pattern char 'B' with locale.providers as
 HOST on macOS for Taiwanese

Reviewed-by: jlu, rriggs
---
 .../provider/HostLocaleProviderAdapterImpl.java     | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/java.base/macosx/classes/sun/util/locale/provider/HostLocaleProviderAdapterImpl.java b/src/java.base/macosx/classes/sun/util/locale/provider/HostLocaleProviderAdapterImpl.java
index e587ee54097..e24a986782d 100644
--- a/src/java.base/macosx/classes/sun/util/locale/provider/HostLocaleProviderAdapterImpl.java
+++ b/src/java.base/macosx/classes/sun/util/locale/provider/HostLocaleProviderAdapterImpl.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 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
@@ -874,6 +874,17 @@ public class HostLocaleProviderAdapterImpl {
             sb.append('\'');
             break;
 
+        case 'B':
+            // 'B' character (day period) is not supported by SimpleDateFormat,
+            // this is a workaround in which 'B' character
+            // appearing in macos' pattern string (based on LDML) is replaced
+            // with 'a' character and hence resolved with am/pm strings.
+            // This workaround is based on the fallback mechanism
+            // specified in LDML spec for 'B' character, when a locale
+            // does not have data for day period ('B')
+            appendN('a', count, sb);
+            break;
+
         default:
             appendN(cldrLetter, count, sb);
             break;