follow-on to r1294180

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1294186 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/poi/ss/util/WorkbookUtil.java

@@ -45,6 +45,29 @@ public class WorkbookUtil {
 	 * @return a valid string, "empty" if to short, "null" if null         
 	 */
 	public final static String createSafeSheetName(final String nameProposal) {
+		return createSafeSheetName(nameProposal, ' ');
+	}
+
+    /**
+     * Creates a valid sheet name, which is conform to the rules.
+     * In any case, the result safely can be used for
+     * {@link org.apache.poi.ss.usermodel.Workbook#setSheetName(int, String)}.
+     * <br>
+     * Rules:
+     * <ul>
+     * <li>never null</li>
+     * <li>minimum length is 1</li>
+     * <li>maximum length is 31</li>
+     * <li>doesn't contain special chars: : 0x0000, 0x0003, / \ ? * ] [ </li>
+     * <li>Sheet names must not begin or end with ' (apostrophe)</li>
+     * </ul>
+     *
+     * @param nameProposal can be any string, will be truncated if necessary,
+     *        allowed to be null
+     * @param replaceChar the char to replace invalid characters.
+     * @return a valid string, "empty" if to short, "null" if null
+     */
+    public final static String createSafeSheetName(final String nameProposal, char replaceChar) {
         if (nameProposal == null) {
             return "null";
         }
@@ -66,11 +89,11 @@ public class WorkbookUtil {
                 case '*':
                 case ']':
                 case '[':
-					result.setCharAt(i, ' ');
+                    result.setCharAt(i, replaceChar);
                     break;
                 case '\'':
                     if (i==0 || i==length-1) {
-						result.setCharAt(i, ' ');
+                        result.setCharAt(i, replaceChar);
                     }
                     break;
                 default: