如何列出 2009 年和 2010 年周一至周四的所有日历日期？

发布于 2024-09-28 10:07:14 字数 189 浏览 0 评论 0原文

我需要向后循环并列出 2009 年和 2010 年每周一至周四的所有日历日期，并将它们记录为映射到一周中某一天的日-月-年字符串映射

"19-10-2010", "Tuesday"
"4-10-2010", "Monday"

： Java 中的库可以帮助解决这个问题，还是可以仅使用标准库来完成？

原文

I need to loop backwards and make a list of all calendar dates in 2009 and 2010 that fall on Monday - Thursday of each week and record them as a map of day-month-year strings mapped to a day of the week:

"19-10-2010", "Tuesday"
"4-10-2010", "Monday"

Is there a library in Java that would help with this or can it be done with just the standard library?

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折戟 2024-10-05 10:07:14

使用日历：

将YEAR 设置为2009
将DAY_OF_YEAR 设置为1
迭代2009、2010 年的所有日期，检查周一至周四。

代码：

Calendar cal = Calendar.getInstance();

// Start in 1 Jan 2009
cal.set(YEAR, 2009);
cal.set(DAY_OF_YEAR, 1);

// Iterate while in 2009 or 2010
while (cal.get(YEAR) <= 2010)
{
    int dow = cal.get(DAY_OF_WEEK);
    if (dow >= Calendar.MONDAY && dow <= Calendar.THURSDAY))
    {
        // add to your map
    }
    cal.add(Calendar.DATE, 1);
}

更新：

对此进行优化很简单，这样您就不需要迭代周五、周六、周日：只要看到周四就添加 4 天，否则添加 1 天：

while (cal.get(YEAR) <= 2010)
{
    int dow = cal.get(DAY_OF_WEEK);
    if (dow >= Calendar.MONDAY && dow <= Calendar.THURSDAY))
    {
        // add to your map
    }
    cal.add(Calendar.DATE, (dow == Calendar.THURSDAY)? 4 : 1);
}

Use a Calendar:

Set YEAR to 2009
Set DAY_OF_YEAR to 1
Iterate over all days in year 2009, 2010 checking for Mon-Thu.

Code:

Calendar cal = Calendar.getInstance();

// Start in 1 Jan 2009
cal.set(YEAR, 2009);
cal.set(DAY_OF_YEAR, 1);

// Iterate while in 2009 or 2010
while (cal.get(YEAR) <= 2010)
{
    int dow = cal.get(DAY_OF_WEEK);
    if (dow >= Calendar.MONDAY && dow <= Calendar.THURSDAY))
    {
        // add to your map
    }
    cal.add(Calendar.DATE, 1);
}

Update:

It is trivial to optimize this so that you don't need to iterate over Fri, Sat, Sun: Just add 4 days whenever you see a Thursday, 1 otherwise:

while (cal.get(YEAR) <= 2010)
{
    int dow = cal.get(DAY_OF_WEEK);
    if (dow >= Calendar.MONDAY && dow <= Calendar.THURSDAY))
    {
        // add to your map
    }
    cal.add(Calendar.DATE, (dow == Calendar.THURSDAY)? 4 : 1);
}

回复收藏 0 原文

阿楠 2024-10-05 10:07:14

您可以利用 guava 的计算图。通过这样做，您不需要生成所有日期及其星期几并保存在内存中。

    ConcurrentMap<String, String> m = new MapMaker()
            .makeComputingMap(new Function<String, String>() {
                Calendar cal = Calendar.getInstance();
                SimpleDateFormat formatDay = new SimpleDateFormat("EEEE");
                SimpleDateFormat format = new SimpleDateFormat("dd-MM-yyyy");
                final String notApplicable = "NA";

                @Override
                public String apply(String arg0) {

                    try {
                        cal.setTime(format.parse(arg0));
                    } catch (ParseException e) {
                        e.printStackTrace();
                    }
                    int dow = cal.get(DAY_OF_WEEK);
                    int year=cal.get(YEAR);
                    if(year!=2009&&year!=2010)
                        return notApplicable;
                    if (dow >= Calendar.MONDAY && dow <= Calendar.THURSDAY) {
                        return formatDay.format(cal.getTime());
                    }
                    return notApplicable;
                }
            });

要获取星期几，您可以执行以下操作：

 m.get("01-01-2009");

You can make use of guava's computing map.By doing so you need not generate all the date's and their day of week and keep in memory.

    ConcurrentMap<String, String> m = new MapMaker()
            .makeComputingMap(new Function<String, String>() {
                Calendar cal = Calendar.getInstance();
                SimpleDateFormat formatDay = new SimpleDateFormat("EEEE");
                SimpleDateFormat format = new SimpleDateFormat("dd-MM-yyyy");
                final String notApplicable = "NA";

                @Override
                public String apply(String arg0) {

                    try {
                        cal.setTime(format.parse(arg0));
                    } catch (ParseException e) {
                        e.printStackTrace();
                    }
                    int dow = cal.get(DAY_OF_WEEK);
                    int year=cal.get(YEAR);
                    if(year!=2009&&year!=2010)
                        return notApplicable;
                    if (dow >= Calendar.MONDAY && dow <= Calendar.THURSDAY) {
                        return formatDay.format(cal.getTime());
                    }
                    return notApplicable;
                }
            });

To get the day of week you can do: