To get the filename you can use this:

EditText fileNameEdit= (EditText) getActivity().findViewById(R.id.fileName);
String fileName = fileNameEdit.getText().toString();

Then write the file on disk:

try {
    String content = "Separe here integers by semi-colon";
    File file = new File(fileName +".csv");
    // if file doesnt exists, then create it
    if (!file.exists()) {
       file.createNewFile();
    }

    FileWriter fw = new FileWriter(file.getAbsoluteFile());
    BufferedWriter bw = new BufferedWriter(fw);
    bw.write(content);
    bw.close();

} catch (IOException e) {
    e.printStackTrace();
}

To read the file:

BufferedReader br = null; 
try {
  String sCurrentLine;
  br = new BufferedReader(new FileReader(fileName+".csv"));
  while ((sCurrentLine = br.readLine()) != null) {
    System.out.println(sCurrentLine);
  }
} catch (IOException e) {
    e.printStackTrace();
} finally {
  try {
     if (br != null)br.close();
  } catch (IOException ex) {
     ex.printStackTrace();
  }
}

Then to have the Integers you can use split function:

String[] intArray = sCurrentLine.split(";");

Try OpenCSV - it will make your life easier.

First, add this package to your gradle dependencies as follows

implementation 'com.opencsv:opencsv:4.6'

Then you can either do

import com.opencsv.CSVReader;
import java.io.IOException;
import java.io.FileReader;


...

try {
    CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
    String[] nextLine;
    while ((nextLine = reader.readNext()) != null) {
        // nextLine[] is an array of values from the line
        System.out.println(nextLine[0] + nextLine[1] + "etc...");
    }
} catch (IOException e) {

}

or

CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
List myEntries = reader.readAll();

Edit after comment

try {
    File csvfile = new File(Environment.getExternalStorageDirectory() + "/csvfile.csv");
    CSVReader reader = new CSVReader(new FileReader(csvfile.getAbsolutePath()));
    String[] nextLine;
    while ((nextLine = reader.readNext()) != null) {
        // nextLine[] is an array of values from the line
        System.out.println(nextLine[0] + nextLine[1] + "etc...");
    }
} catch (Exception e) {
    e.printStackTrace();
    Toast.makeText(this, "The specified file was not found", Toast.LENGTH_SHORT).show();
}

If you want to package the .csv file with the application and have it install on the internal storage when the app installs, create an assets folder in your project src/main folder (e.g., c:\myapp\app\src\main\assets\), and put the .csv file in there, then reference it like this in your activity:

String csvfileString = this.getApplicationInfo().dataDir + File.separatorChar + "csvfile.csv"
File csvfile = new File(csvfileString);

I have something like this;

public final List<String[]> readCsv(Context context) {
  List<String[]> questionList = new ArrayList<String[]>();
  AssetManager assetManager = context.getAssets();

  try {
    InputStream csvStream = assetManager.open(CSV_PATH);
    InputStreamReader csvStreamReader = new InputStreamReader(csvStream);
    CSVReader csvReader = new CSVReader(csvStreamReader);
    String[] line;

    // throw away the header
    csvReader.readNext();

    while ((line = csvReader.readNext()) != null) {
      questionList.add(line);
    }
  } catch (IOException e) {
    e.printStackTrace();
  }
  return questionList;
}

Try with this code snippet :

  String baseDir = android.os.Environment.getExternalStorageDirectory().getAbsolutePath();
  String fileName = "AnalysisData.csv";
  String filePath = baseDir + File.separator + fileName;
  File f = new File(filePath);
  CSVWriter writer;

  // File exist
  if(f.exists()&&!f.isDirectory())
    {
      mFileWriter = new FileWriter(filePath, true);
      writer = new CSVWriter(mFileWriter);
    }
  else
    {
      writer = new CSVWriter(new FileWriter(filePath));
    }

    String[] data = {"Ship Name", "Scientist Name", "...", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").formatter.format(date)});

  writer.writeNext(data);

  writer.close();

There are file explorer style apps that will open it. Or you could download Csv Viewer app from Play Store.

Blurb from it.

CSV File Viewer For Android | CSV Reader - view small and large-sized CSV files.

CSV Reader - Simple, fast, and powerful tool for reading csv files.

I am not associated with it.