Scanner unable to read foreign characters in file

Question

I'm currently creating a tool that can extract and search for data stored on a smartwatch for a University project.

I have been able to extract a file in particular called "Node.db" from my smartwatch which contains the Bluetooth MAC Address of the mobile phone the smartwatch is connected to. I am now trying to create a scanner than will scan this "node.db" file and print out the MAC Address.

This is the code I currently have:

// Identify the location of the node.txt file    
File file = new File("C:\\WatchData\\node.txt");
// Notify the user that Bluetooth extraction has initalized
Txt_Results.append("Pulling bluetooth data...");
        Scanner in = null;
        try {
            in = new Scanner(file);
            while(in.hasNext())
            {   // Scan till the end of the file
                String line=in.nextLine();
                // Scan the file for this string
                if(line.contains("settings.bluetooth"))
                // Print the MAC Address string out for the user
                    System.out.println(line);
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }      

A previous function converted the file to .txt. The code searches each line and looks for "settings.bluetooth" and should print out this line which contains the MAC Address if it is found. However, I believe the format of the node.db file is stopping the scanner from finding this string. I believe that some of the data in the file is encoded. An example of how the data is presented is shown below. I believe it is the black characters it doesn't recognize:

When I run the code on the file, the program will simply hang and provide no error message. I have left the program to run for over 20 minutes and still no success.

The exact line I am trying to print out from the file is shown below:

I have tested this code on a text file without these encoded characters and can conclude that the code does work. So my question is the following:

Is there a way that I can get the scanner to skip the characters it doesn't recognize in the file so it can continue scanning the file?

Thanks in advance.

Answer 1

Since you didn't provide the files here, so I can't write code to test on your files. It looks like your files have an different encoding than that Java uses to decode it.

So, you need to try different encoding settings for your input stream.

Usually, you specify the encoding by:

String encoding = "UTF-8"; // try "UTF-8" first and also change to other encodings to see the results
Reader reader = new InputStreamReader(new FileInputStream("your_file_name"), encoding);

Refer to this post for more information. This post also talks about how to write code to detect the encoding of your file.

BTW, the decoded characters shown in your file with a dark background are some control characters in ASCII.

I would also suggest you try changing the decoding method of your text viewer application to see if you can actually make the text display correctly in a particular encoding method.

UPDATE

It looks like Scanner doesn't work while using other IO class actually works fine.

StringBuilder sb = new StringBuilder();

try (BufferedReader reader = new BufferedReader(new FileReader("node.txt"))) {

    String line;
    while ((line = reader.readLine()) != null) {
        sb.append(line);
    }

} catch (Exception e) {
    // TODO: handle exception
}


int index = sb.indexOf("settings.bluetooth");
if (index != -1)
    System.out.println(sb.substring(index, index + 18));

UPDATE

It looks like only when you create a Scanner from a File will cause an exception in one of the Scanner's inner method when reading from the file. But using an input stream as below will always work, even wrapping it inside a Scanner.

try (Scanner s = new Scanner(new FileInputStream("node.txt"))) {
    while(s.hasNext()) {
        System.out.println(s.next());
    }
} catch (Exception e) {
    e.printStackTrace();
}

UPDATE

This solution just eliminates all the illegal characters from your file.

public static void main(String args[]) {
    String encoding = "UTF-8"; // try "UTF-8" first and also change to other encodings to see the results

    StringBuilder sb = new StringBuilder();
    try(Reader reader = new InputStreamReader(new FileInputStream("node.txt"), encoding)) {
        int c = -1;
        while ((c = reader.read()) != -1) {
            if (eligible(c)) {
                sb.append((char)c);
            }
        }
    } catch (Exception e){
        e.printStackTrace();
    }

    int index = sb.indexOf("settings.bluetooth");
    if (index >= 0) {
        System.out.println(sb.substring(index));
    }
}

public static boolean eligible(int c) {
    return (c >= 'a' && c <= 'z' || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || c == '.');
}