// date為"2018-01-27"形式
public static float getJ(String date){

int year = 0;
int MM = 0;
int dd = 0;
try {
    Date sdf = new SimpleDateFormat("yyyy-MM-dd").parse(date);

    SimpleDateFormat sdf0 = new SimpleDateFormat("yyyy");
    SimpleDateFormat sdf1 = new SimpleDateFormat("MM");
    SimpleDateFormat sdf2 = new
 
 SimpleDateFormat("dd");
//      擷取年份
    String str0 = sdf0.format(sdf);
//      擷取月份
    String str1 = sdf1.format(sdf);
//      擷取日
    String str2 = sdf2.format(sdf);

//      轉int型別
    year = Integer.parseInt(str0);
    MM = Integer.parseInt(str1);
    dd = Integer.parseInt(str2);

    } catch (ParseException e) {
        e.printStackTrace();
    }

//      J  ---為儒略日，取值範圍為1到365或366;
 

    int J =0;
    for (int i = 1; i < MM; i++) {
        J = getJ(year, i, dd);
    }
    return J;
}

//能被4整除且不能被100整除或者能被400整除的年份為閏年
    public static int getJ(int year,int month,int day) {
        int totalDay=0;
        for(int i=1;i<month;i++){
            totalDay+=getMonthDay(year,i);
        }
        int
 
 J = totalDay+day;
        return J;

    }

    public static int getMonthDay(int year,int month){
        boolean flag=isRunnian(year);
        if(month==2){
            if(flag==true){
                return 29;
            }else{
                return 28;
            }
        }else if(month==4||month==6||month==9||month==11){
            return 30;
        }else{
            return 31;
        }
    }

    public static boolean isRunnian(int year){
        if((year%4==0&&year%100!=0)||(year%400==0)){
            return true;
        }else{
            return false;
        }

    }