Question

i have this sample list from a file

firstname, lastname, age
anne, smith, 6
dougie, miller, 8

right now i am stuck with the arraylist

ArrayList<String[]> rows = new ArrayList<>();
     while ((line = reader.readLine()) != null) {
        String[] row = line.split(",");
        rows.add(row);
    }

    for (String[] row : rows) {
        System.out.println(Arrays.toString(row));
    }

and i got these output:

[firstname,lastname,age]
[anne,smith,6]
[dougie,miller,8]

i have tried using doing this:

String[] x1 = new String[rows.size()+1];
     for(int i=0;i<rows.size();i++){
     String[] lastname = (String[]) rows.get(i+1);
        System.out.println(lastname[1]);
        //x1[i]=lastname[1];
     }

but i couldn’t seem to put the lastname in one array. it will give me this error:

Exception in thread “AWT-EventQueue-0” java.lang.IndexOutOfBoundsException: Index: 227, Size: 227

i want to have this output:

firstname
anne
dougie

lastname
smith
miller

age
6
8

how do i do that?

Answer 1

This one should work fine, provided the StringArrays are all same sized:

int cols = rows.size() > 0 ? rows.get(0).length : 0;
for (int i = 0; i < cols; i++) {
  for (int j = 0; j < rows.size(); j++) {
    System.out.println(rows.get(j)[i]);
  }
}