added getStringValue method

poi-util/src/main/java/de/muehlencord/shared/poi/PoiUtil.java

@@ -144,6 +144,23 @@ public abstract class PoiUtil {
         currentCell.setCellValue(date);
     }
 
+    /**
+     * Returns the string value from the given cell. If the value is mandatory but the cell does not contain a value a {@link PoiException} is thrown.
+     *
+     * @param row the row to read the value from
+     * @param cellNumber the cellnumber (starting with 0) of the {@link Row} to read the content from.
+     * @param mandatory if set to true, a {@link PoiException} is thrown, if the specified cell, does not contain any value. Otherwise null is returned if the cell is empty.
+     * @return the String value of the specified cell.
+     * @throws PoiException if the cell value cannot be read or if the cell is empty and mandatory has been set to true.
+     */
+    public static String getStringValue(Row row, int cellNumber, boolean mandatory) throws PoiException {
+        String returnValue = getStringValue(row, cellNumber, false, null);
+        if (returnValue == null) {
+            throw new PoiException("Value in row=" + row.getRowNum() + ", cell=" + cellNumber + " is mandatory but not available");
+        }
+        return returnValue;
+    }
+
     public static String getStringValue(Row row, int cellNumber) throws PoiException {
         return getStringValue(row, cellNumber, false, null);
     }
@@ -239,8 +256,7 @@ public abstract class PoiUtil {
     }
 
     /**
-     * remove charecters which often cause troubles in other applications - e.g.
+     * remove charecters which often cause troubles in other applications - e.g. em dash (long dash) is created by Excel automatically
-     * em dash (long dash) is created by Excel automatically
      *
      * @param sourceValue the input string to execute the replacement
      * @return sourceValue with replaced characters