Writing large data using Apache POI

[Srikanth Kumar]

I am trying to write 20000 records in an excel sheet using Apache POI. When i try to do this the process is taking more than 7 minutes. Sometimes i even get the java.lang.OutOfMemoryError. my code simply writes the data retrieved from the database to the excel sheet.

        int counter = sheet.getPhysicalNumberOfRows() + 1;
        while (resultset.next()) {
           row = sheet.createRow((short) counter++);
 
            completeFileName = resultset.getString("...");
 
            if (completeFileName != null
                    && completeFileName.indexOf(SLASH) >= 0) {
                filePath = completeFileName.substring(0,
                        completeFileName.lastIndexOf(SLASH));
                fileName = completeFileName.substring(completeFileName
                        .lastIndexOf(SLASH) + 1);
            } else {
                fileName = completeFileName;
            }
            cell = row.createCell((short) 0);
            cell.setCellValue(filePath);
 
            cell = row.createCell((short) 1);
            cell.setCellValue(fileName);
            
            cell = row.createCell((short) 2);
            cell.setCellValue(
                    resultset.getString("..."));
            
            object = resultset.getTimestamp("...");
            if (object != null) {
            cell = row.createCell((short)3);
            cell.setCellValue(
                        df.format((Timestamp)object));
            } else {
            cell = row.createCell((short) 3);
            cell.setCellValue("");
            }
            cell = row.createCell((short) 4);
            cell.setCellValue(
                    resultset.getInt("..."));
            cell = row.createCell((short) 5);
            cell.setCellValue(
                    resultset.getString("..."));
            
            object = resultset.getTimestamp("...");
            
            if(object != null){
            cell = row.createCell((short) 6);
            cell.setCellValue(
                        df.format((Timestamp)object));
            }else{
            cell = row.createCell((short) 6);
            cell.setCellValue("");
            }
            cell = row.createCell((short) 7);
            cell.setCellValue(
                    resultset.getInt("..."));
            cell = row.createCell((short) 8);
            cell.setCellValue(
                    resultset.getString("..."));
        }

I dint understand the problem in the code. is anything going wrong?
Thanks in advance.

[ November 25, 2008: Message edited by: Srikanth Kumar ]
[ November 27, 2008: Message edited by: Martijn Verburg ]

[Ulf Dittmer]

POI is known to need a lot of memory (the reason for that is most likely the OLE document format, which is quite complex). Can you allocate a larger heap size to the JVM?