How to read a file in Java and save each item

Question

I have a text file with integers and double number like this:

16 -122.454803 41.923870
17 -122.440536 41.946377
18 -122.440498 41.956013

I have 3 lists(one int and two double lists) and i want to save the items from each column. How can i split the items and save them in the lists?

ArrayList<Integer> list1 = new ArrayList<Integer>();
    ArrayList<Double> list2 = new ArrayList<Double>();
    ArrayList<Double> list3 = new ArrayList<Double>();

    BufferedReader in = new BufferedReader(new FileReader("Nodes.txt"));

    String line;
    while((line = in.readLine()) != null){
        list1.setNodeId(line.split(" "));
        System.out.println(line);
    }
    in.close();

Answer 1

One way to process the data:

String line;
while ((line = reader.readLine()) != null) {
    String[] parts = line.split(" ");
    if (parts.length != 3) {
        continue;
    }
    list1.add(Integer.parseInt(parts[0]));
    list2.add(Double.parseDouble(parts[1]));
    list3.add(Double.parseDouble(parts[2]));
}

However: this code lacks error checking on the data type. And I guess you need to process the data afterwards, so I highly suggest that you write a GeoPosition class (just a name guess from the data) with the index and position fields and a parse(String) method to parse each line. A list of such elements is much easier to process afterwards in comparison to 3 separate lists.

Answer 2

You can do something like this:

public static void main(String[] args) {

    // TODO Auto-generated method stub

    ArrayList<Integer> list1 = new ArrayList<Integer>();
    ArrayList<Double> list2 = new ArrayList<Double>();
    ArrayList<Double> list3 = new ArrayList<Double>();

    BufferedReader in;
    String line;
    try {
        in = new BufferedReader(new FileReader("Nodes.txt"));
          while((line = in.readLine()) != null){
               System.out.println(line);
               String arr[] = line.split(" ");

               list1.add(Integer.valueOf(arr[0]));
               list2.add(Double.valueOf(arr[1]));
               list3.add(Double.valueOf(arr[2]));
          }
            in.close();
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    for (int i = 0; i < list1.size(); i++){
        System.out.println(list1.get(i));
    }

    for (int i = 0; i < list2.size(); i++){
        System.out.println(list2.get(i));
    }

    for (int i = 0; i < list3.size(); i++){
        System.out.println(list3.get(i));
    }

}

Answer 3

String.split returns an array of Strings. You need to take appropriate array entry and convert it to desired value type

        String[] entries = line.split(" ");
        list1.add(Integer.valueOf(entries[0]));
        list2.add(Double.valueOf(entries[1]));
        list3.add(Double.valueOf(entries[2]));

Answer 4

You can try by this way ;)

ArrayList<Integer> list1 = new ArrayList<Integer>();
ArrayList<Double>  list2 = new ArrayList<Double>();
ArrayList<Double>  list3 = new ArrayList<Double>();

Path path = Paths.get("C:/User/.../.../.../nodes.txt");

Scanner in = new Scanner(path);
double line;

while(in.hasNextDouble()){
    line = in.nextDouble();
    list1.add((int)line);

    line = in.nextDouble();
    list2.add(line);

    line = in.nextDouble();
    list3.add(line);


     System.out.println(line);
}
in.close();

Don't forget to write the correct path, and tell if it's working ;)

edit : be careful, i tried and "15.05" is not working with my method, it needs "15,05", i think it will be the same with the post just over mine