android - null exception when writing file to internal storage from separate class -

i have 2 activities want call time class bellow every time call class throws exception. if put timewrite() method in activity works if put in time class , try call write file throws exception.

public class time extends alphabetactivity{       private int time;       public void timewrite(int time) {         try {           string timeval = string.valueof(time);           fileoutputstream timestream = openfileoutput("time_file.txt",    context.mode_private);         timestream.write(timeval.getbytes());}         timestream.close();        catch (exception e) {         e.printstacktrace();}} 

it seems wrong inheritance , not understanding doing wrong.

   try {       string timeval = string.valueof(time);       fileoutputstream timestream = openfileoutput("time_file.txt",    context.mode_private);     timestream.write(timeval.getbytes()); }     timestream.close();    catch (exception e) {     e.printstacktrace();} } 

your code compile if write:

 try {   string timeval = string.valueof(time);   fileoutputstream timestream = openfileoutput("time_file.txt",    context.mode_private);       timestream.write(timeval.getbytes());       timestream.close();      }catch (exception e) {       e.printstacktrace();     } 

if think sytanx wrong, code compile ? please read this, know, long have study or later: https://docs.oracle.com/javase/tutorial/essential/exceptions/

same http://www.tutorialspoint.com/java/java_exceptions.htm

if write file external storge, mind add read , write_external_storage permission manifest