Reading double values from a file

Question

I\'m trying to read some numbers (double) from a file and store them in an ArrayList and an array (yes, I need both) with the code below:

try {
    Scanner s         


        

Answer 1

I had the same problem (not working scanner) and the solution seems to be surprisingly easy. You just need to set a locale for it.

  // use US locale to be able to identify doubles in the string
  scanner.useLocale(Locale.US);

taken from here: http://www.tutorialspoint.com/java/util/scanner_nextdouble.htm

Answer 2

I tried reducing the code down to only test the Scanner by itself. The following code works with your data file:

public static void main(String[] args) {
    Scanner scan;
    File file = new File("resources\\scannertester\\data.txt");
    try {
        scan = new Scanner(file);

        while(scan.hasNextDouble())
        {
            System.out.println( scan.nextDouble() );
        }

    } catch (FileNotFoundException e1) {
            e1.printStackTrace();
    }

}

I got the following (expected) output:

0.0
0.0
0.023
0.023
0.05
0.05
0.2
0.2
0.5
0.5
0.8
0.8
0.95
0.95
0.977
0.977
1.0
1.0

Try this to make sure you're referencing the correct file.

Answer 3

Below is my rendition of your code, adapted to make it run. It immediately explodes with an array indexing exceptions.

So: Can you give us a little more framework? What's different from what I did?

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public class Zenzen {

   private static ArrayList<Double> tmp = new ArrayList<Double>();

   private static File file = new File("Zenzen.dat");

   public static void main(String[] args) {

      Scanner scan;
      try {
         scan = new Scanner(file);
         Object[][] tmp2 = new Object[tmp.size() / 2][2];
         int tmp3 = 0;

         while (scan.hasNextDouble()) {
            tmp.add(scan.nextDouble());
            System.out.println(Arrays.deepToString(tmp.toArray())); // debug print
            for (int i = 0; i < tmp.size() / 2; i++) {
               for (int j = 0; j < 2; j++) {
                  tmp2[i][j] = tmp.get(tmp3);
                  tmp3++;
               }
            }
         }

      } catch (FileNotFoundException fnfe) {
         fnfe.printStackTrace();
      }
   }
}

---

[0.0]
[0.0, 0.0]
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
    at Zenzen.main(Zenzen.java:26)

Answer 4

Try setting the delimiter first:

scan.useDelimiter("\\s+");

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