Gerorianischer Kalender wechselt am Freitag die Woche Warum

[Joob]

Nicht nur das die Wochenzahlen falsch sind, er wechselt auch am Freitag die Woche.
Wie kann ich ihm sagen das Montag die Woche beginnt ?

Folgender Code:

        GregorianCalendar gc = new GregorianCalendar(); 
            System.out.println("first day : " + gc.getFirstDayOfWeek());
        gc.setFirstDayOfWeek(GregorianCalendar.MONDAY);
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 1);
        int week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 1.1: " + week);
        
            
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 3);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 4.1: " + week);
            
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 4);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 4.1: " + week);
              
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 7);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 7.1: " + week);
        
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 8);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 8.1: " + week);
        
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 9);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 9.1: " + week);
                    
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 10);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 10.1: " + week);
                    
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 11);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 11.1: " + week);
            
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 12);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 12.1: " + week);
        
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 13);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 13.1: " + week);
        
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 14);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 14.1: " + week);
                    
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 15);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 15.1: " + week);
                    
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 16);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 16.1: " + week);
        
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 17);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 17.1: " + week);
                    
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 18);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 18.1: " + week);
                    
        gc.set(GregorianCalendar.YEAR, 2019);
        gc.set(GregorianCalendar.MONTH, 1);
        gc.set(GregorianCalendar.DATE, 19);
        week = gc.get(GregorianCalendar.WEEK_OF_YEAR);   
            System.out.println("Week 19.1: " + week);

Bei mir kommt folgendes raus, darauf kann ich mir keinen Reim machen.

first day : 2
Week 1.1: 5
Week 4.1: 5
Week 4.1: 6
Week 7.1: 6
Week 8.1: 6
Week 9.1: 6
Week 10.1: 6
Week 11.1: 7
Week 12.1: 7
Week 13.1: 7
Week 14.1: 7
Week 15.1: 7
Week 16.1: 7
Week 17.1: 7
Week 18.1: 8
Week 19.1: 8

 

[httpdigest]

Bitte ließ die Dokumentation von GregorianCalendar und Calendar, insbesondere von MONTH.
Heißt:

gc.set(GregorianCalendar.YEAR, 2019);
gc.set(GregorianCalendar.MONTH, 1);
gc.set(GregorianCalendar.DATE, 4);

Setzt den Kalender auf den 04.02.2019, was ein Montag war!

 

[Joob]

Danke, 0 based hab ich nicht gesehen.