java - remove black diamond with a question mark text from android sdcard file -

i creating listview json data.when user offline want show data in listview. have stored json data in android sdcard. , retrive data when user offline , showed in listview. problem is, when read file directory it's show's me black diamond question mark , stores in array list. type of "����t��*" question how remove type of string arraylist. please help

save data:

 public  void savemydata() {     try {         objectoutput out = new objectoutputstream(new fileoutputstream(new file(getfilesdir(),"")+"cachefile.txt"));         out.writeobject(al.tostring());         toast.maketext(getapplicationcontext(), "data saved..",toast.length_long).show();         out.close();     } catch (ioexception e) {         e.printstacktrace();     } } 

this retrieving code.

string filecontent = "";     try {         string currentline;         bufferedreader bufferedreader;         fileinputstream fileinputstream = new fileinputstream(getfilesdir()+"cachefile.txt");         bufferedreader = new bufferedreader(new inputstreamreader(fileinputstream,"utf-8"));           while ((currentline = bufferedreader.readline()) != null) {             filecontent += currentline + '\n';         }          bufferedreader.close();     } catch (ioexception e) {         e.printstacktrace();          log.d("failed","thos null");         filecontent = null;     }     log.d("sucess","sucess buddyy"+filecontent); 

broadly speaking, issue you're using objectoutputstream write data file, bufferedreader read in. objectoutputstream designed allow objects , native data types written stream in way can read in via objectinputstream reconstitute objects in same way. encoding not meant human readable , contains characters field separators.

i don't know al is, since you're calling tostring() before write it, can assume want actual strings in file can read. this, want use printstream , printstream.println() method instead of objectoutputstream.