Fix bug #51273 - Hash codes can be negative when working on our own low memory hash for formula cell evaluation

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1128268 13f79535-47bb-0310-9956-ffa450edef68

src/documentation/content/xdocs/status.xml

@@ -34,6 +34,7 @@
 
     <changes>
         <release version="3.8-beta3" date="2011-??-??">
+           <action dev="poi-developers" type="fix">51273 - Formula Value Cache fix for repeated evaluations</action>
            <action dev="poi-developers" type="add">51171 - Improved performance of SharedValueManager </action>
            <action dev="poi-developers" type="fix">51236 - XSSF set colour support for black/white to match getter</action>
            <action dev="poi-developers" type="add">51196 - Initial support for Spreadsheet Chart API</action>

src/java/org/apache/poi/ss/formula/FormulaCellCacheEntrySet.java

@@ -76,8 +76,7 @@ final class FormulaCellCacheEntrySet {
 
 
 	private static boolean addInternal(CellCacheEntry[] arr, CellCacheEntry cce) {
-
-		int startIx = cce.hashCode() % arr.length;
+		int startIx = Math.abs(cce.hashCode() % arr.length);
 
 		for(int i=startIx; i<arr.length; i++) {
 			CellCacheEntry item = arr[i];
@@ -130,7 +129,7 @@ final class FormulaCellCacheEntrySet {
 		// else - usual case
 		// delete single element (without re-hashing)
 
-		int startIx = cce.hashCode() % arr.length;
+		int startIx = Math.abs(cce.hashCode() % arr.length);
 
 		// note - can't exit loops upon finding null because of potential previous deletes
 		for(int i=startIx; i<arr.length; i++) {