Removing row in CSV file

Question

I have created an ArrayList called entryList. The method I am trying to create is that if you write removeAllByDate() and enter a date, the entire line with that date should be removed. The entryList in turn consists of entries (rows) and I have also created the method getDate(). I thought of writing something like this:

public void removeAllByDate(String datum) {
    for(Entry entry: entryList) {
        if (entry.getDate().contains(datum)) {
            entryList.remove(entry);
        }
    }
}

Does anyone see why this does not work?

The `entryList` is the data that is already present in the CSV and you need to delete some of the data ? — Trishul Singh Choudhary, Mar 01 '20 at 11:14
@Melissa Loos The getDate() method only consists of return this.date — Nickewas, Mar 01 '20 at 11:17
@Nickewas Hope you understand that you can't remove the data from csv where the data is already present. You can only create a new file which does not contain the data you want to remove. — Trishul Singh Choudhary, Mar 01 '20 at 11:34
@TrishulSinghChoudhary Oh, I may not have been clear about this but I am creating a new csvfile by stroring all the data from the old one and then writing it over to a new document, and this method is meant to do changes to that new document ie not containing the row with the specified date — Nickewas, Mar 01 '20 at 11:37

score 1 · Answer 1 · answered Mar 01 '20 at 15:48

Since Java 8, the method to use when conditionally removing elements from a Collection is removeIf(). Your code will be as simple as the following:

entryList.removeIf(entry -> entry.getDate().contains(datum));

The original code is not working because removal of elements is not allowed while iterating over the collection, see this question and answers.

Dave The Dane · Answer 2 · 2020-03-01T12:06:15.183

Nickewas, you're not being very forthcoming with Information:
- there are at least 2 different ArrayLists (e.g. java.util.ArrayList & java.util.Arrays.ArrayList)
- you don't mention how it doesn't work!

It may possibly be something to do with the following:
the for-each-loop uses an Iterator provided by your Iterable (entryList).
Maybe entryList.remove(entry) is having a side-effect on the Iterable?

Maybe this, or a variation thereof, would do it?

entryList.stream()
    .filter (entry -> entry.contains  (datum))  // Creates filtered Stream which...
    .forEach(entry -> entryList.remove(entry)); // ...maybe removes side-effect?

If not, you might have to use a Collector & iterate over the resulting List.

Removing row in CSV file

2 Answers2