JavaIO

public void read(View view) {
        try {
            FileInputStream fileInputStream= openFileInput("myText.txt");
            InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            StringBuffer stringBuffer = new StringBuffer();
            String lines;
            while ((lines=bufferedReader.readLine())!=null) {
                stringBuffer.append(lines+"\n");
            }
            textView.setText(stringBuffer.toString());
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void write(View view) {
        String Mytextmessage  = editText.getText().toString();
        try {
            FileOutputStream fileOutputStream = openFileOutput("myText.txt",MODE_PRIVATE);
            fileOutputStream.write(Mytextmessage.getBytes());
            fileOutputStream.close();
            Toast.makeText(getApplicationContext(),"Text Saved",Toast.LENGTH_LONG).show();
            editText.setText("");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }