From d1490896ed2488d32ccf06ee2d8c4eb5b32ffdde Mon Sep 17 00:00:00 2001
From: Robin Leroy <egg.robin.leroy@gmail.com>
Date: Thu, 18 Jul 2024 15:48:57 +0200
Subject: [PATCH] ICU-22707 Fix an ancient bug in moveIndex32

---
 .../test/java/com/ibm/icu/dev/test/rbbi/RBBITestMonkey.java   | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/rbbi/RBBITestMonkey.java b/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/rbbi/RBBITestMonkey.java
index 66f7a94024a..40791d38037 100644
--- a/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/rbbi/RBBITestMonkey.java
+++ b/icu4j/main/core/src/test/java/com/ibm/icu/dev/test/rbbi/RBBITestMonkey.java
@@ -2093,8 +2093,8 @@ public class RBBITestMonkey extends CoreTestFmwk {
                 }
                 pos--;
                 c = s.charAt(pos);
-                if (UTF16.isTrailSurrogate(c) && pos >= 0) {
-                    c = s.charAt(pos);
+                if (UTF16.isTrailSurrogate(c) && pos > 0) {
+                    c = s.charAt(pos - 1);
                     if (UTF16.isLeadSurrogate(c)) {
                         pos--;
                     }