与JAVA中的Oracle next_day函数等效

如何解决与JAVA中的Oracle next_day函数等效

我想制作一个类似于oracle的next_day()函数的方法，以下是我的代码，该代码在MONDAY，TUESDAY等接受n个工作日的日期，并返回从输入日期。

/**
 * @param date
 * @param weekDay
 * @return Gives the date for next weekday specified in the parameter.
 */    
public Date getNextDay(Date value,String weekday) {
    Calendar date1 = Calendar.getInstance();
    date1.setTime(value);
        
    if (weekday.equalsIgnoreCase("MONDAY")) {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.MONDAY) {
            date1.add(Calendar.DATE,1);
        }
    } else if (weekday.equalsIgnoreCase("TUESDAY")) {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.TUESDAY) {
            date1.add(Calendar.DATE,1);
        }
    } else if (weekday.equalsIgnoreCase("WednESDAY")) {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.WednESDAY) {
            date1.add(Calendar.DATE,1);
        }
    } else if (weekday.equalsIgnoreCase("THURSDAY")) {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.THURSDAY) {
            date1.add(Calendar.DATE,1);
        }
    } else if (weekday.equalsIgnoreCase("FRIDAY")) {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.FRIDAY) {
            date1.add(Calendar.DATE,1);
        }
    } else if (weekday.equalsIgnoreCase("SATURDAY")) {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY) {
            date1.add(Calendar.DATE,1);
        }
    } else {
        while (date1.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY) {
            date1.add(Calendar.DATE,1);
        }
    }
                
    return date1.getTime();
}

请提出一种更好的方法。

解决方法

我建议您使用modern java.time日期时间API进行操作。从 Trail: Date Time 了解有关现代日期时间API的更多信息。 java.util日期时间API和SimpleDateFormat已过时且容易出错。如果您不使用Java-8，则仍可以通过ThreeTenABP库使用Java-8日期时间API。

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;

public class Main {
    public static void main(String[] args) {
        // Tests

        // Next occurrence
        System.out.println(getNextDay(LocalDate.now(),"Monday"));
        System.out.println(getNextDay(LocalDate.now(),"Wednesday"));

        // Same (if date falls on the given day) or next occurrence
        System.out.println(getSameOrNextDay(LocalDate.now(),"Monday"));
        System.out.println(getSameOrNextDay(LocalDate.now(),"Wednesday"));
    }

    static LocalDate getNextDay(LocalDate value,String weekday) {
        return value.with(TemporalAdjusters.next(DayOfWeek.valueOf(weekday.toUpperCase())));
    }

    static LocalDate getSameOrNextDay(LocalDate value,String weekday) {
        return value.with(TemporalAdjusters.nextOrSame(DayOfWeek.valueOf(weekday.toUpperCase())));
    }
}

输出：

2020-09-28
2020-09-30
2020-09-28
2020-09-23

,

如果您对第二天感兴趣，我建议您使用java.time.LocalDate而不是java.util.Date。

以下代码接受LocalDate这样的String（必须是一周中的一整天，用大写字母表示），并返回代表最近日期的LocalDate星期几：

public static LocalDate nextDay(LocalDate sourceDay,String weekday) {
    // parse the day of week to an enum value
    DayOfWeek dayOfWeek = DayOfWeek.valueOf(weekday);
    // check if the day is the same as the one of the given LocalDate
    if (sourceDay.getDayOfWeek().equals(dayOfWeek)) {
        // and return the LocalDate that's a week later
        return sourceDay.plusWeeks(1);
    } else {
        // otherwise add a day to the given date
        LocalDate nextDayOfWeek = sourceDay.plusDays(1);
        // and do that until the day of week of the given date is reached
        while (nextDayOfWeek.getDayOfWeek() != dayOfWeek) {
            nextDayOfWeek = nextDayOfWeek.plusDays(1);
        }
        // then return the future date
        return nextDayOfWeek;
    }
}

您可以像这样在main中使用它：

    public static void main(String[] args) {
        System.out.println(nextDay(LocalDate.now(),"FRIDAY")
                            .format(DateTimeFormatter.ofPattern("uuuu-MM-dd '('EEEE')'",Locale.ENGLISH)));
    }

输出（今天 ⇒2020-09-23）：

2020-09-25 (Friday)

,

使用“新”的java.time.DayOfWeek和java.time.LocalDate类：

public LocalDate getNextDay(
    final LocalDate value,final DayOfWeek day
)
{
    int currentDay = value.getDayOfWeek().getValue();
    int expectedDay = day.getValue();
    if ( currentDay >= expectedDay )
    {
        expectedDay += 7;
    }
    return value.plusDays( expectedDay - currentDay );
}