Java中的 DayOfWeek from() 方法及示例

Java .time.DayOfWeek的from()方法是Java中的一个内置函数，它接受定义日期的 TemporalAccessor 并返回对应于该日期的 DayOfWeek 实例。 TemporalAccessor 表示任意日期和时间信息集，此方法将其转换为对应于该日期的 DayOfWeek 实例。

方法声明：

public static DayOfWeek from(TemporalAccessor temporal)

句法：

DayOfWeek dayOfWeekObject = DayOfWeek.from(TemporalAccessor temporal)

参数：此方法将时间作为参数，其中：

temporal –是一个表示日期的 TemporalAccessor。

dayOfWeekObject –是 DayOfWeek 的一个实例。

返回值：该函数返回一个 DayOfWeek 实例，对应temporal指定的日期

下面的程序说明了上述方法：
方案一：

// Java Program Demonstrate from()
// method of DayOfWeek
  
import java.time.*;
import java.time.DayOfWeek;
  
class DayOfWeekExample {
    public static void main(String[] args)
    {
        // Set a local date whose day is found
        LocalDate localDate
            = LocalDate.of(1997, Month.AUGUST, 15);
  
        // Initialize a DayOfWeek object
        // with specified local Date
        DayOfWeek dayOfWeek
            = DayOfWeek.from(localDate);
  
        // Printing the day of the week
        System.out.println("Day of the Week on "
                           + localDate + " - "
                           + dayOfWeek.name());
    }
}

输出：

Day of the Week on 1997-08-15 - FRIDAY

方案二：

// Java Program Demonstrate from()
// method of DayOfWeek
  
import java.time.*;
  
class DayOfWeekExample {
    public static void main(String[] args)
    {
        // Set a local date whose day is found
        LocalDate localDate
            = LocalDate.of(2015, Month.JULY, 13);
  
        // Initialize a DayOfWeek object
        // with specified local Date
        DayOfWeek dayOfWeek
            = DayOfWeek.from(localDate);
  
        // Printing the day of the week
        System.out.println("Day of the Week on "
                           + localDate + " - "
                           + dayOfWeek.name());
    }
}

输出：

Day of the Week on 2015-07-13 - MONDAY

参考： https: Java/time/DayOfWeek.html#from-java.time.temporal.TemporalAccessor-