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); }
