Write and read floats from internal storage

Question

I need to store three pairs of floats (three points coordinates) in file, then read them and compare. I tried this way:

public Path loadPath()
{
    Path path = new Path();
    float x, y;
    try
    {
        FileInputStream fis = new FileInputStream(filePath);
        DataInputStream dis = new DataInputStream(fis);
        for(int i = 0; i < 3; i++)
        {
            x = dis.readFloat();
            y = dis.readFloat();
            path.addCircle(x, y, rad, Path.Direction.CW);
        }
        dis.close();
    }
    catch (FileNotFoundException e)
    {
        e.printStackTrace();
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }


    return path;
}

public void savePath(Path cPath)
{
    PathMeasure pm = new PathMeasure(cPath, false);
    float coords[] = {0f, 0f};
    try
    {
        FileOutputStream fos = new FileOutputStream(filePath);
        DataOutputStream dos = new DataOutputStream(fos);
        do
        {
            pm.getPosTan(pm.getLength() * 0.5f, coords, null);
            dos.writeFloat(coords[0]);
            dos.writeFloat(coords[1]);
        }
        while(pm.nextContour());
        dos.close();
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }
}

But DataOutputStream writes in binary format and I get this in my file:

BК CF BК CF BК CF

So when DataInputStream tries read this, it gets something strange. I also tried to write with FileWriter, file contents looks fine, but I can't propertly read floats out there.

What need I use to write/read floats property?

The DataOutputStream is used to serialize data to a stream (and in your case down to a file). Regardless of what you're passing to it, be it writeUTF(), writeShort() or writeFloat() it will translate into a stream of bytes. Are you asking for a human readable file with something like 1.23, 1.01, 234.9989 etc? — britzl, May 28 '13 at 10:29
@shoe rat, no, SharedPreferences does not approach, because I will use more points in future — a_dobryn, May 28 '13 at 10:33
@britzl, doesn't matter, any way to be able to read them later — a_dobryn, May 28 '13 at 10:35
what you've done now should work. Write with a DataOutputStream and read with a DataInputStream. When you say that you get "BK CF BK CF" etc, what do you mean? Are you opening the file in Notepad or something? — britzl, May 28 '13 at 11:49
@britzl yes, I've copied the resulting file from emulator and opened it in FreeCommander's viewer in binary mode. Hmm. I don't know how,but now it works propertly O_o magic! or emulator bug — a_dobryn, May 28 '13 at 12:41

score 0 · Accepted Answer · answered Jun 30 '15 at 13:01

Use a Scanner and a Formatter from the java.util library. You can use this object to create and write multiple data types to files. Here's an example:

package pckge.name.goes.here;

import java.io.*;
import java.util.*;

public class Main {

    private static Formatter writer;
    private static Scanner input;

    private static void openFileForWriting(String file) {
        try {
            writer = new Formatter(file);
        } catch(Exception e) {
            System.err.println("Couldn't create file!");
        }
    }

    private void openFileForReading(String file) {
        try {
            input = new Scanner(new File(file));
        } catch(Exception e) {
            System.err.println("Couldn't find file!");
        }
    }

    private void closeFileForWriting() {
        writer.close();
    }

    private void closeFileForReading() {
        input.close();
    }

    private void writeFloat(float f) {
        writer.format("%f%n", f);
    }

    private float[] readCooridnates(String xyz) {
        float[] coordinates = new float[2];
        int position = 0;

        while(scanner.hasNext()) {
            switch(xyz) {
            case "x":

                switch(position) {
                case 0:
                    coordinates[position] = Float.parseFloat(scanner.next());
                    break;
                case 1:
                    coordinates[position] = Float.parseFloat(scanner.next());
                    break;
                default:
                    //Do nothing
                    break;
                }

                break;
            case "y":
                switch(position) {
                case 2:
                    coordinates[position] = Float.parseFloat(scanner.next());
                    break;
                case 3:
                    coordinates[position] = Float.parseFloat(scanner.next());
                    break;
                default:
                    //Do nothing
                    break;
                }
                break;
            case "z":
                switch(position) {
                case 4:
                    coordinates[position] = Float.parseFloat(scanner.next());
                    break;
                case 5:
                    coordinates[position] = Float.parseFloat(scanner.next());
                    break;
                default:
                    //Do nothing
                    break;
                }
                break;
            default:
                //Do nothing
                break;
            }

            position++;
        }

        return coordinates;
    }
}

Write and read floats from internal storage

1 Answers1