Question

我是Java的新手，我正在尝试获取2009年的第7天。我对如何处理感到困惑。下面是我的代码

public class Main {

    public static void main(String[] args) {
        System.out.println("WELCOME TO MY CALENDER CLASS");

        Calendar calendar = Calendar.getInstance();

        calendar.set(DAY_OF_MONTH,7);
        calendar.set(Calendar.YEAR,2009);

        for(int i =1; i <= 12; i++){
            calendar.set(DAY_OF_MONTH,i);
            System.out.println(calendar.getTime());
        }
    }
}

更新：这是我的结果

Sun Mar 01 23:41:14 GMT 2009 
Mon Mar 02 23:41:14 GMT 2009 
Tue Mar 03 23:41:14 GMT 2009 
Wed Mar 04 23:41:14 GMT 2009 
Thu Mar 05 23:41:14 GMT 2009 
Fri Mar 06 23:41:14 GMT 2009 
Sat Mar 07 23:41:14 GMT 2009 
Sun Mar 08 23:41:14 GMT 2009 
Mon Mar 09 23:41:14 GMT 2009 
Tue Mar 10 23:41:14 GMT 2009 
Wed Mar 11 23:41:14 GMT 2009 
Thu Mar 12 23:41:14 GMT 2009

Answer 1

好的，假设您从1月1日开始，这是您原因的简单示例。我希望Java1.8代码对您来说很清楚。

public static void main(String[] args) {
        // create two localdate start of a year instances, one for current year and one for next year, 2009 and 2010 respectively
        LocalDate thisYear = LocalDate.of(2009, Month.JANUARY, 1);
        LocalDate nextYear = LocalDate.of(2010, Month.JANUARY, 1);
        // used only for counting number of every seventh day in a year
        int i=0;
        // while we are not in the next year, 2010
        while (thisYear.isBefore(nextYear)) {
            i++;
            // print current date
            System.out.println(i+" " + thisYear.toString());
            // add a week or seven days to our thisYear instance and loop thru again
            thisYear = thisYear.plusWeeks(1);
        }

    }

Answer 2

您的代码存在的问题是，在for循环中，您为Calendar对象设置了日期而不是月份。
因此更改为：

for(int i = 0; i < 12; i++){
    calendar.set(Calendar.MONTH, i);
    System.out.println(calendar.getTime());
}

循环从0开始到11，因为月份是从0开始的。
如果您可以使用LocalDate，那么您的代码将更加简单和高效：

System.out.println("WELCOME TO MY CALENDER CLASS");

LocalDate date;
for(int i = 1; i <= 12; i++){
    date = LocalDate.of(2009, Month.of(i), 7);
    System.out.println(date.format(DateTimeFormatter.ofLocalizedDate(FormatStyle.FULL)));
}

我如何从1月到12月的某一天

2 个答案: