android - Java adding week to date -

this question has answer here:

• modify week in calendar 4 answers

my code should add 1 week each time runs when setting jaar 2015 , week 50 , running following code multiple times:

gregoriancalendar cal = new gregoriancalendar(); cal.set(calendar.year, jaar); cal.set(calendar.week_of_year, week); cal.add(calendar.week_of_year, 1); jaar = cal.get(calendar.year); week = cal.get(calendar.week_of_year); log.d("jaar", integer.tostring(jaar)); log.d("week", integer.tostring(week)); 

the output is:

jaar: 2015 week: 51  jaar: 2015 week: 52  jaar: 2016 week: 53  jaar: 2017 week: 2  jaar: 2017 week: 3 

so code not working. please help.

edit:

the codes run when user presses icon in tool bar:

public static int jaar; public static int week;    public gregoriancalendar cal = new gregoriancalendar();   @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);      gregoriancalendar calendar2 = new gregoriancalendar();            bundle extras = getintent().getextras();         if(extras == null) {             week = 50;              jaar = calendar2.get(calendar.year);          } else {              week = extras.getint("week");             jaar = extras.getint("jaar");          } }      if (id == r.id.action_volgende) {         cal.set(calendar.year, jaar);         cal.set(calendar.week_of_year, week);          cal.add(calendar.week_of_year, 1);         jaar = cal.get(calendar.year);         week = cal.get(calendar.week_of_year);         log.d("jaar", integer.tostring(jaar));         log.d("week", integer.tostring(week));         intent i=new intent(mainactivity.this,mainactivity.class);         i.putextra("week", week);         i.putextra("jaar", jaar);         startactivity(i);         finish(); 

check values of week , year each time code executes. ran following code similar yours, not exactly, , works expect:

    int jaar = 2015;     int week = 50;      gregoriancalendar cal = new gregoriancalendar();     cal.set(calendar.year, jaar);     cal.set(calendar.week_of_year, week);      while(true) //loop adds 1 week.      {      cal.add(calendar.week_of_year, 1);     jaar = cal.get(calendar.year);     week = cal.get(calendar.week_of_year);      system.out.println("jaar: " + jaar);     system.out.println("week: " + week);     } 

results in:

jaar: 2015 week: 51

jaar: 2015 week: 52

jaar: 2016 week: 1

jaar: 2016 week: 2