string - Android Studio Saving Data to Phone -

string mystring = "hello world"; 

how save contents of mystring .txt file within phone/android, there after application ends , can edit value in future?

use method:

public void writetofile(string str)     try {             outputstreamwriter outputstreamwriter = new outputstreamwriter(context.openfileoutput("config.txt", context.mode_private));             outputstreamwriter.write(data);             outputstreamwriter.close();         }         catch (ioexception e) {             log.e("exception", "file write failed: " + e.tostring());         } private string readfromfile() {      string ret = "";      try {         inputstream inputstream = openfileinput("config.txt");          if ( inputstream != null ) {             inputstreamreader inputstreamreader = new inputstreamreader(inputstream);             bufferedreader bufferedreader = new bufferedreader(inputstreamreader);             string receivestring = "";             stringbuilder stringbuilder = new stringbuilder();              while ( (receivestring = bufferedreader.readline()) != null ) {                 stringbuilder.append(receivestring);             }              inputstream.close();             ret = stringbuilder.tostring();         }     }     catch (filenotfoundexception e) {         log.e("login activity", "file not found: " + e.tostring());     } catch (ioexception e) {         log.e("login activity", "can not read file: " + e.tostring());     }      return ret; }