How to delete, not clear row in Sheet ? Apache POI

Question

I don't know how to delete row without leaving an empty row.

I am using Apache POI 3.9 and I am getting an error using the following code:

public List<MeterInfo> addToList(String patternt) throws ParseException, IOException {
    List<Object> data = new ArrayList<Object>();
    int lastRowNum = sheet.getLastRowNum();
    Row row;
    for(int i = 0; i < lastRowNum; i++){
        row = sheet.getRow(i);
        if(patternt.equals(getCurrentString(row))){
            data.add(getDataFromRow(row));
            sheet.removeRow(row);
            sheet.shiftRows(row.getRowNum() + 1, row.getRowNum() + 1, -1);
        }
    }
    saveWorkbook(new File("blabla.xlsx"));
    return data;
}

I've found a solution in https://stackoverflow.com/a/3554129/6812826, but I am getting a NullPointerException because I am decreasing lastRowNum by each deleted row.

Here is the new version:

public List<Object> addToList(String pattern) throws ParseException, IOException {
    List<Object> data= new ArrayList<Object>();
    for (int i = 0; i <= sheet.getLastRowNum(); i++) {
        Row row = sheet.getRow(i);
        if (pattern.equals(getCurrentString(row))) {
            data.add(getMeterInfo(row));
            deleteRow(row);
        }
    }
    saveWorkbook(new File("blabla.xlsx"));
    return data;
}

private void deleteRow(Row row) {
    int lastRowNum = sheet.getLastRowNum();
    int rowIndex = row.getRowNum();
    if(rowIndex >= 0 && rowIndex < lastRowNum){
        sheet.shiftRows(rowIndex + 1, lastRowNum, -1);
    }
    if(rowIndex == lastRowNum){
        Row removingRow = sheet.getRow(rowIndex);
        if(removingRow != null){
            sheet.removeRow(removingRow);
        }
    }
}

Answer 1

Try this code, it should work:

for(int i = 0; i < sheet.getLastRowNum(); i++)
{
    row = sheet.getRow(i);
    if(patternt.equals(getCurrentString(row)))
    {
        data.add(getDataFromRow(row));
        // sheet.removeRow(row);    NO NEED FOR THIS LINE
        sheet.shiftRows(row.getRowNum() + 1, sheet.getLastRowNum() + 1, -1);
        i--;
    }
}

You need to decrease i by one every time you delete one row. And get the last row number again by using getLastRowNum().