From 2c7e5e4b29c80d5475e971232458d3481bbe7136 Mon Sep 17 00:00:00 2001
From: XenoAmess <xenoamess@gmail.com>
Date: Mon, 25 May 2020 21:41:18 +0800
Subject: [PATCH] [LANG-1545] CharSequenceUtils.regionMatches is wrong dealing
 with Georgian. (#529)

* CharSequenceUtils.regionMatches is wrong dealing with Georgian.
see details in tests.
* refine tests
---
 .../commons/lang3/CharSequenceUtils.java      |  7 ++---
 .../apache/commons/lang3/StringUtilsTest.java | 27 +++++++++++++++++++
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/src/main/java/org/apache/commons/lang3/CharSequenceUtils.java b/src/main/java/org/apache/commons/lang3/CharSequenceUtils.java
index 58c04536e..fdb91220b 100644
--- a/src/main/java/org/apache/commons/lang3/CharSequenceUtils.java
+++ b/src/main/java/org/apache/commons/lang3/CharSequenceUtils.java
@@ -294,9 +294,10 @@ public class CharSequenceUtils {
                 return false;
             }
 
-            // The same check as in String.regionMatches():
-            if (Character.toUpperCase(c1) != Character.toUpperCase(c2)
-                    && Character.toLowerCase(c1) != Character.toLowerCase(c2)) {
+            // The real same check as in String.regionMatches():
+            char u1 = Character.toUpperCase(c1);
+            char u2 = Character.toUpperCase(c2);
+            if (u1 != u2 && Character.toLowerCase(u1) != Character.toLowerCase(u2)) {
                 return false;
             }
         }
diff --git a/src/test/java/org/apache/commons/lang3/StringUtilsTest.java b/src/test/java/org/apache/commons/lang3/StringUtilsTest.java
index 30263de6b..cea53a263 100644
--- a/src/test/java/org/apache/commons/lang3/StringUtilsTest.java
+++ b/src/test/java/org/apache/commons/lang3/StringUtilsTest.java
@@ -3305,4 +3305,31 @@ public class StringUtilsTest {
             Locale.setDefault(defaultLocales);
         }
     }
+
+    @Test
+    public void testGeorgianSample() {
+        char[] arrayI = new char[]{
+                //Latin Small Letter dotless I
+                (char) 0x0131,
+                //Greek Capital Letter Theta
+                (char) 0x03F4
+        };
+        char[] arrayJ = new char[]{
+                //Latin Capital Letter I with dot above
+                (char) 0x0130,
+                //Greek Theta Symbol
+                (char) 0x03D1
+        };
+        for (char i : arrayI) {
+            for (char j : arrayJ) {
+                String si = "" + i;
+                String sj = "" + j;
+                boolean res1 = si.equalsIgnoreCase(sj);
+                CharSequence ci = new StringBuilder(si);
+                CharSequence cj = new StringBuilder(sj);
+                boolean res2 = StringUtils.startsWithIgnoreCase(ci, cj);
+                assertEquals(res1, res2, "si : " + si + " sj : " + sj);
+            }
+        }
+    }
 }