java 一年中过去的日子，直到那一年的日期。

Posted 2021-05-07

//Gives back the number of days that have passed since the begining of a year.
//1-365.
public static int dayOfYear(String date) {
        int[] daysInMonth = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        String[] dateArr = date.trim().split("-");
        int year = Integer.parseInt(dateArr[0]);
        int month = Integer.parseInt(dateArr[1]);
        int day = Integer.parseInt(dateArr[2]);
        if(leapYear(year)) daysInMonth[1] = 29;
        
        int total = 0;
        for(int i = 0; i < month; i++){
            total += daysInMonth[i];
        }
        total+=day;
        return total;
    }
    
    public static boolean leapYear(int year){
        boolean leap = false;
        if(year % 4 == 0)
        {
            if( year % 100 == 0)
            {
                // year is divisible by 400, hence the year is a leap year
                if ( year % 400 == 0)
                    leap = true;
                else
                    leap = false;
            }
            else
                leap = true;
        }
        else
            leap = false;
        if(leap)
            return true;
        else
            return false;
    }