Need to delete empty columns in csv

Question

I have created CSV file using Open CSV library using some run time data coming from different datasource.

Now I am looking a lot of empty columns which doesn't have value in column cells and so I want to delete that programmatically.

Approach I am currently trying to implement is, get first CSV data in String 2 dimensional array and iterate it vertically and do something to delete empty columns!

Is any other better approach I can follow? Pls suggest!

Regards

//edited

Code for writing in CSV using OpenCSV library:

public static void writeDataToCSV(CSVWriter writer, String[][] csvData){
    List<String[]> csvDataList = new ArrayList<String[]>();
    for (String[] rowData : csvData) {
        csvDataList.add(rowData);
    }
    writer.writeAll(csvDataList);
}

What do you mean by "Deleting" ? Removing them from the 2D String array or from the csv file ? — DeadlyJesus, Jan 15 '15 at 15:34
Then read it as a 2D string array, and rewrite the csv without including the empty columns. — DeadlyJesus, Jan 15 '15 at 15:37
Can you add the code that you're using to write the CSV file (`CSVWriter`)? — Ascalonian, Jan 15 '15 at 15:42
find edit in my post for csv write code! If before writing to CSV, If I update string 2d array, then it is possible what I need, means when I open csv, it will not show empty columns! — S Singh, Jan 15 '15 at 15:51
Note, you cannot drop an entry from the middle of a list, if you want to edit it in place, you want to make it a list or array of `LinkedList`s. — Konstantin Tarashchanskiy, Jan 15 '15 at 15:53
Do you know ahead of time which columns you want to delete or do you need to do a check before hand before deleting? — Ascalonian, Jan 15 '15 at 16:21

Ascalonian · Answer 1 · 2015-01-15T16:28:18.670

So in the provided String[], you know what index of the column you need to remove, correct? If so, you can do this:

for (String[] rowData : csvData) {
    // Convert the String[] to an ArrayList to be able to easily remove the specific column
    ArrayList<String> rowArray = new ArrayList<String>(Arrays.asList(rowData));

    // Remove that specific column value
    rowArray.remove(<index of column>);

    // Convert the ArrayList back into an array so it can be written to the CSV
    String[] dataToWrite = rowArray.toArray(new String[rowArray.size()]);

    // Add it to the ArrayList of values to be written
    csvDataList.add(dataToWrite);
}

Konstantin Tarashchanskiy · Answer 2 · 2015-01-15T17:04:55.003

0

Did not actually run this, so some errors may exist, but the rough skeleton should be:

int height;  //How many rows
int width;  //How many columns per row

Set<Integer> emptyCols = new HashSet<Integers>();  //Columns that are empty

for (int x = 0; x < width; x++) { //Look at each column
  boolean empty = true; //We have yet to find an item in this column
  for (int y = 0; y < height; y++) {
    if (!data[y][x].isEmpty()) {  //This column is not empty, we can move on
      empty = false;
      break;
    }
  }

  if (empty) {
    emptyCols.add(x);
  }
}

for (int y = 0; y < height; y++) {
  for (int x = 0; x < width; x++) {
    if (!emptyCols.contains(x)) {
      //write out data[y][x]
    }
  }
  //Terminate row
}

edited Jan 15 '15 at 17:04

answered Jan 15 '15 at 15:50

Konstantin Tarashchanskiy

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@Tom Thanks for catching that – Konstantin Tarashchanskiy Jan 15 '15 at 16:49
Your last `if` statement is still missing the parenthesis :) – Ascalonian Jan 15 '15 at 16:54
@Ascalonian I was, now I am not. Thanks for the catch. – Konstantin Tarashchanskiy Jan 15 '15 at 17:05

Need to delete empty columns in csv

2 Answers2