Question

What I need to achieve is to import data from a text file that contains two columns of doubles as follows:

201.0176    1.06E+03
201.7557    1.11E+01
202.0201    2.02E+02
202.2064    9.76E+00
202.8342    1.11E+01
203.0161    2.02E+02
203.1638    9.61E+00
203.3843    1.13E+01

There are up to about 50,000 lines of these data. I want each column to be imported into a separate array but I cannot work out how to identify between the separate columns. I have tried the following:

public class CodeTests {

    public static ArrayList assignArray(String filePath) throws FileNotFoundException {
        Scanner s = new Scanner(new File(filePath));
            ArrayList<Double> list = new ArrayList<Double>();
            while (s.hasNext()){
                list.add(s.nextDouble());
            }
            s.close();
            return list;
    }

    public static void main(String[] args) throws IOException {
        /*
         * 
         */
        ArrayList arrayMZ;
        arrayMZ = assignArray("F:/Stuff/Work/Work from GSK/From Leeds/ja_CIDFragmenter/testFile.txt");

        for(int i = 0; i < arrayMZ.size(); i++)
            System.out.println(arrayMZ.get(i));
        System.out.println("End");
    }
}

From running this I get the output:

run:
201.0176
1060.0
201.7557
11.1
202.0201
202.0
202.2064
9.76
202.8342
11.1
203.0161
202.0
203.1638
9.61
203.3843
11.3
End
BUILD SUCCESSFUL (total time: 1 second)

Can anyone help me either separate these columns into two arrays or even into a single 2D array under the columns of array[0] with the first data column in it and array[1] with the second. i.e. :

  [0]         [1]
201.0176    1.06E+03
201.7557    1.11E+01
202.0201    2.02E+02
202.2064    9.76E+00
202.8342    1.11E+01
203.0161    2.02E+02
203.1638    9.61E+00
203.3843    1.13E+01

I’ve tried to make this as clear as I can but if there is anything else please let me know.

Thanks

Answer 1

You could do something like this:

public static ArrayList[] assignArray(String filePath) throws FileNotFoundException {
    Scanner s = new Scanner(new File(filePath));
        ArrayList[] list = new ArrayList[2];
        ArrayList<Double> col1 = new ArrayList<Double>();
        ArrayList<Double> col2 = new ArrayList<Double>();
        while (s.hasNext()){
            String[] data = s.nextLine().split("\\s+"); 
            col1.add(Double.parseDouble(data[0]));
            col2.add(Double.parseDouble(data[1]));
        }
        s.close();
        list[0] = col1;
        list[1] = col2;
        return list;
}

and obtain an array of two ArrayList with your data.