java.util.ConcurrentModificationException while removing row from Excel in java

Question

for(Row row:sheet) {
  for(int rowNo=0;rowNo<sheet.getLastRowNum();rowNo++) {
    row=sheet.getRow(rowNo);
    sheet.removeRow(row);
  }
}

I am trying to remove the rows from Excel file through java but it is giving me error

java.util.ConcurrentModificationException at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1207) at java.util.TreeMap$ValueIterator.next(TreeMap.java:1252)

You look to be looping through the rows twice in the two for loops. Anyhow, it's the implicit iterator in the outer enhanced for loop which is complaining because you are changing the rows in the inner for loop. — Andy Turner, Oct 05 '15 at 13:38

score 1 · Answer 1 · answered Oct 05 '15 at 13:39

1

TreeMap does not support concurrent removals.

You should use iterator's remove method

Iterator<Row> it = sheet.iterator();
while(it.hasNext())
{
    Row row = it.next();
    ... 
    it.remove();
}

answered Oct 05 '15 at 13:39

James Wierzba

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hii James Wierzba, This is also not working giving me the same error – Swapnil Chidrawar Oct 05 '15 at 13:44
Can you explain why you loop over the rows twice? Are you excluding some code? – James Wierzba Oct 05 '15 at 13:47
Actually we are processing one workbook which contain 27 sheets so i need to remove the 9th sheet rows and add new logic to write the data – Swapnil Chidrawar Oct 05 '15 at 13:50

score 0 · Answer 2 · answered Oct 05 '15 at 13:42

0

You don't appear to be using the row from the outer for loop, so you can remove it:

for(int rowNo=sheet.getLastRowNum()-1; rowNo >= 0;rowNo--) {
  row=sheet.getRow(rowNo);
  sheet.removeRow(row);
}

Note also that I'm iterating the rows backwards, so you don't end up only removing every other row.

answered Oct 05 '15 at 13:42

Andy Turner

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hii Andy Turner this solution is also not working – Swapnil Chidrawar Oct 05 '15 at 13:47
Please explain "Not working". Did you remove the outer loop? – Andy Turner Oct 05 '15 at 13:48
Actually we are processing one workbook which contain 27 sheets so i need to remove the 9th sheet rows and add new logic to write the data – Swapnil Chidrawar Oct 05 '15 at 13:52
That doesn't explain what "not working" means. – Andy Turner Oct 05 '15 at 13:52
not working means its giving me the same error as previous – Swapnil Chidrawar Oct 05 '15 at 13:53

java.util.ConcurrentModificationException while removing row from Excel in java

2 Answers2