Java 输入两个日期，计算出期间的周数

只要涉及到其他周的天，都算期间的周数：

    static int calculate(Calendar c){
        int dayForWeek;
        if(c.get(Calendar.DAY_OF_WEEK) == 1){
            dayForWeek = 7;
        }else{
            dayForWeek = c.get(Calendar.DAY_OF_WEEK) - 1;}
        return dayForWeek;
    }

    static Calendar From(Calendar c){
        switch(calculate(c)){
            case 1:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)-0);
                break;
            case 2:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)-1);
                break;
            case 3:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)-2);
                break;
            case 4:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)-3);
                break;
            case 5:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)-4);
                break;
            case 6:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)-5);
                break;
            case 7:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)-6);
        }
        return c;

    }

    static Calendar To(Calendar c){
        switch(calculate(c)){
            case 1:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)+6);
                break;
            case 2:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)+5);
                break;
            case 3:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)+4);
                break;
            case 4:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)+3);
                break;
            case 5:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)+2);
                break;
            case 6:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)+1);
                break;
            case 7:c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR)+0);
        }
        return c;

    }


    static Long getResult(String startDate,String endDate) throws ParseException {
        Calendar c1 = Calendar.getInstance();
        Calendar c2 = Calendar.getInstance();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");

        c1.setTime(sdf.parse(startDate));
        c2.setTime(sdf.parse(endDate));

        long cc1=From(c1).getTimeInMillis()/(1000*3600*24);
        long cc2=To(c2).getTimeInMillis()/(1000*3600*24);

        return (cc2-cc1+1)/7;
    }

测试：

 

刚好一周：

    public static void main(String[] args) throws ParseException {

        Long result = getResult("2020-02-10", "2020-02-16");
        System.out.println("涉及的周数为："+result);

    }

 

 

刚好两周：

    public static void main(String[] args) throws ParseException {

        Long result = getResult("2020-02-10", "2020-02-23");
        System.out.println("涉及的周数为："+result);

    }

 

两周再多两天：

    public static void main(String[] args) throws ParseException {

        Long result = getResult("2020-02-10", "2020-02-25");
        System.out.println("涉及的周数为："+result);

    }