Question

如何使用java.util.Calendar获得特定月份的日子。我已经尝试了下面给出的代码，但是它给了我最近一个月的日期，而不是我所输入的月份。 我不想使用开关盒。 谁能帮忙吗？预先感谢！

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

    Calendar cal = Calendar.getInstance();
    int month = cal.get(Calendar.MONTH);
    int year = cal.get(Calendar.YEAR);


    if (month == 0) {
        month = 3;
        year = year-1;
    }

    String dateStart = "'" + (year) + "-" + (month) + "-1 00:00:00'";
    String dateEnd = "'" + (year) + "-" + (month) + "-" 
                            + cal.getMaximum(Calendar.DAY_OF_MONTH);
    dateEnd = dateEnd + " 23:59:59'";
    System.out.println("Start and End Date : " + dateStart + " : " + dateEnd);
}

Answer 1

这是一个如何使用int month获得给定int year和java.time的日子的示例，
看看评论：

import java.time.LocalDate;
import java.time.YearMonth;
import java.time.format.DateTimeFormatter;
import java.time.format.TextStyle;
import java.util.Locale;
import java.util.Set;
import java.util.TreeSet;
import java.util.stream.IntStream;

public class Main {

    public static void main(String[] args) {
        int month = 1;
        int year = 2018;

        // create something that stores the days and keeps them sorted, preferably
        Set<LocalDate> allDaysOfGivenMonth = new TreeSet<LocalDate>();

        // stream the days from first to last day of the given month
        IntStream.rangeClosed(1, YearMonth.of(year, month).lengthOfMonth())
                .mapToObj(day -> LocalDate.of(year, month, day)) // map them to LocalDate objects
                .forEach(localDate -> allDaysOfGivenMonth.add(localDate)); // and store each of them

        // afterwards, just print them for a first glance...
        allDaysOfGivenMonth.forEach(localDate -> {
            System.out.println(localDate.format(DateTimeFormatter.ISO_LOCAL_DATE) + " - " 
                    + localDate.getDayOfWeek()
                                .getDisplayName(TextStyle.FULL_STANDALONE, Locale.getDefault()));
        });
    }

}

Answer 2

我在上面的评论中使用了这种逻辑，但我不理解其背后的逻辑，谁能为我解释一下它的逻辑

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

        Calendar cal = Calendar.getInstance();
        int month = cal.get(Calendar.MONTH);
        int year = cal.get(Calendar.YEAR);


        if(month == 0){
            month = 6;
            year = year-1;
        }
        String dateStart = "'"+(year)+"-"+(month)+"-1 00:00:00'";
            cal.set(Calendar.MONTH, 5);
            cal.set(Calendar.DAY_OF_MONTH, 6);
            cal.set(Calendar.YEAR, 2019);
        String dateEnd = "'"+(year)+"-"+(month)+"-"+cal.getActualMaximum(Calendar.DAY_OF_MONTH);
        dateEnd = dateEnd+" 23:59:59'";
        System.out.println("Start and End Date : "+dateStart+" : "+dateEnd);
    }

获取特定月份的日子

2 个答案: