I tried page break feature of POI-2.5-FINAL, and got trouble.
I create a new workbook file with Excel and call HSSFSheet#getRowBreaks(), then 
it raises NullPointerException.

(1) create a new workbook file (three sheets and no data) with Excel.
I tried with Excel 2000 and XP.
(2) create HSSFWorkbook instance for (1)'s workbook.
(3) call workbook.getSheetAt() to get sheet.
(4) call sheet.getRowBreaks(). It raises NPE.

Environments:
  Windows2000
  J2SE 1.4.2_03
  MS Excel2000
  POI-2.5-FINAL


Here is the stack trace.
---
java.lang.NullPointerException
	at org.apache.poi.hssf.model.Sheet.getNumRowBreaks(Sheet.java:2764)
	at org.apache.poi.hssf.usermodel.HSSFSheet.getRowBreaks(HSSFSheet.java:
1144)
	at POISample.handleSheet(POISample.java:41)
	at POISample.main(POISample.java:26)
Exception in thread "main" 
---

and sample code
---
public class POISample
{

  public static void main(final String[] args)
    throws Exception
  {
    final HSSFWorkbook book = new HSSFWorkbook(new FileInputStream(args[0]));
    POISample.handleSheet(book.getSheetAt(0));
    book.write(new FileOutputStream(args[1]));
  }

  private static void handleSheet(final HSSFSheet sheet)
  {
    for (int i = 0; i < 5; ++i)
    {
      final HSSFRow row = sheet.createRow(i);
      for (short j = 0; j < 5; ++j)
      {
        final HSSFCell cell = row.createCell(j);
        cell.setCellValue(i + ":" + j);
      }
    }
    final int[] breaks = sheet.getRowBreaks();
    sheet.setRowBreak(1);
  }

}
---

Additionally, in some cases i succeeded calling getRowBreaks().
If the sheet already has some page breaks, or the sheet is created with 
HSSFWorkbook#createSheet(), it succeeds.

kind regards.

IRIE Hironori