How to read this from file and get each value alone

Question

I have this text file and I need to extract it to a Java program to determine array sizes and its values I can read each line alone but I can't get the value for lines that contains many numbers. Plus, how to count element in the third line.( 0 2 )

4
5
0 2

0 1 0.6
0 2 0.2
0 3 0.5
1 3 0.8
2 3 0.3

this code that I'm using:

 List<Integer> list = new ArrayList<Integer>();
        File file = new File("D:\\ALGORTHIMS\\MASTER LEVEL\\dr. khaled\\assignment 1\\text.txt");
        BufferedReader reader = null;
         List<Double> ints = new ArrayList<Double>();

        try {
            reader = new BufferedReader(new FileReader(file));
            String text = null;

            while ((text = reader.readLine()) != null) {
                if (text.length() == 1) {
                    list.add(Integer.parseInt(text));
                } else {


                    String[] strs = text.trim().split("\\s+");


                    for (int i = 0; i < strs.length; i++) {
                        ints.add(Double.parseDouble(strs[i]));
                    }
                }
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {

            }
        }

//print out the list
        System.out.println(list);

        System.out.println(ints);

Answer 1

It looks like you are using doubles mixed with int so Integer.parseInt() will not work.

What you could do is to split the line, separated by a space into an array, and put each of those elements into list. Note that this will print 0 as 0.0.

while ((text = reader.readLine()) != null) {
      String[] numbers = text.split(" ");
      for (String number : numbers) {
           list.add(Double.valueOf(number));
      }
}

Also, did you just copy this answer for your code?

Answer 2

Try something like

public static void main(String[] args) {
        List<Double> list = new ArrayList<>();
        File file = new File("text.txt");
        BufferedReader reader = null;

        try {
            reader = new BufferedReader(new FileReader(file));
            String text = null;

            while ((text = reader.readLine()) != null) {
                String[] str = text.split(" ");
                for (int i = 0; i<str.length; i++) {
                    if(str[i].trim().length() > 0) {
                        list.add(Double.parseDouble(str[i]));
                    }
                }
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                System.out.print(e);
            }
        }

//print out the list
        System.out.println(list);
    }

Answer 3

I think that using Scanner is optimal solution. E.g. in case we have file

4 5

 0  1  2  3.1
 4  5  6  7.2
 8  9 10 11.3
12 13 14 15.4
16 17 18 19.5

where we define an array with 4 row and 5 columns. Then to get it in int[][] arr we could use following approach:

public static void main(String... args) throws FileNotFoundException {
    double[][] arr = null;

    try (Scanner scan = new Scanner(new FileInputStream(new File("text.txt")))) {
        scan.useLocale(Locale.US);  // to use '.' as separator
        int rows = scan.nextInt();
        int columns = scan.nextInt();
        scan.nextLine();

        arr = new double[rows][columns];

        for (int i = 0; i < rows; i++)
            for (int j = 0; j < columns; j++)
                arr[i][j] = scan.nextDouble();
    }

    System.out.println(Arrays.toString(arr));
}

Answer 4

You can use java.util.scanner to parse various data types from a stream relatively painlessly.

For example, suppose you wanted to parse the following:

1 2 3.0
4.0 5 6

You could use the following snippet:

Scanner scan = new Scanner(System.in);
int one = scan.nextInt();
int two = scan.nextInt();
double three = scan.nextDouble();
// Defaultly, it will continue past the line break
double four = scan.nextDouble();

// We can also do this
double five = scan.nextDouble();
long six = scan.nextLong();

An important note is that java.util.Scanner will suppress IOExceptions (although, exceptions from converting text, e.g. NumberFormatExceptions, will still be raised). You can check ioException to see if one has been suppressed.