From 6d6089eee5756f472f330a4d2860cf46d921a23c Mon Sep 17 00:00:00 2001
From: PJ Fanning <pjfanning@users.noreply.github.com>
Date: Fri, 5 Dec 2025 10:51:57 +0100
Subject: [PATCH] nullSafeFormatProperties (#961)

---
 .../main/java/org/apache/poi/ss/util/CellUtil.java  | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/poi/src/main/java/org/apache/poi/ss/util/CellUtil.java b/poi/src/main/java/org/apache/poi/ss/util/CellUtil.java
index b8de646192..faa1722b73 100644
--- a/poi/src/main/java/org/apache/poi/ss/util/CellUtil.java
+++ b/poi/src/main/java/org/apache/poi/ss/util/CellUtil.java
@@ -614,7 +614,7 @@ public final class CellUtil {
         CellStyle originalStyle = cell.getCellStyle();
 
         CellStyle newStyle = null;
-        EnumMap<CellPropertyType, Object> values = originalStyle.getFormatProperties();
+        EnumMap<CellPropertyType, Object> values = nullSafeFormatProperties(originalStyle);
         if (properties.containsKey(CellPropertyType.FILL_FOREGROUND_COLOR_COLOR) && properties.get(CellPropertyType.FILL_FOREGROUND_COLOR_COLOR) == null) {
             values.remove(CellPropertyType.FILL_FOREGROUND_COLOR);
         }
@@ -635,7 +635,7 @@ public final class CellUtil {
 
         for (int i = 0; i < numberCellStyles; i++) {
             CellStyle wbStyle = workbook.getCellStyleAt(i);
-            EnumMap<CellPropertyType, Object> wbStyleMap = wbStyle.getFormatProperties();
+            EnumMap<CellPropertyType, Object> wbStyleMap = nullSafeFormatProperties(wbStyle);
 
             // the desired style already exists in the workbook. Use the existing style.
             if (styleMapsMatch(wbStyleMap, values, disableNullColorCheck)) {
@@ -653,6 +653,13 @@ public final class CellUtil {
         cell.setCellStyle(newStyle);
     }
 
+    // try to get format properties from CellStyle but the method may return null
+    // in some implementations, so we need to be null safe here
+    private static EnumMap<CellPropertyType, Object> nullSafeFormatProperties(CellStyle style) {
+        EnumMap<CellPropertyType, Object> props = style.getFormatProperties();
+        return props == null ? getFormatProperties(style) : props;
+    }
+
     private static boolean styleMapsMatch(final Map<CellPropertyType, Object> newProps,
                                           final Map<CellPropertyType, Object> storedProps, final boolean disableNullColorCheck) {
         final EnumMap<CellPropertyType, Object> map1Copy = new EnumMap<>(newProps);
@@ -888,7 +895,7 @@ public final class CellUtil {
         if (src == null || dest == null) {
             throw new IllegalArgumentException("Source and destination styles must not be null");
         }
-        EnumMap<CellPropertyType, Object> properties = src.getFormatProperties();
+        EnumMap<CellPropertyType, Object> properties = nullSafeFormatProperties(src);
         setFormatProperties(dest, destWorkbook, properties);
     }