Java中的即时 getLong() 方法和示例

Instant 类的getLong(TemporalField field)方法用于从该时刻获取作为参数传递的指定字段的长值。此方法在此瞬间查询字段的值，返回的值将始终在该字段的有效值范围内。当该字段不受支持且方法无法返回 int 值时，将引发异常。

句法：

public int getLong(TemporalField field)

参数：此方法接受一个参数字段，即要获取的字段。它不应该为空。

返回：此方法返回字段的长值。

异常：此方法抛出以下异常：

• DateTimeException ：如果无法获取该字段的值或该值超出该字段的有效值范围。
• UnsupportedTemporalTypeException ：如果该字段不受支持或值的范围超过一个 int。
• ArithmeticException : 如果发生数值溢出。

下面的程序说明了 Instant.getLong() 方法：

方案一：

// Java program to demonstrate
// Instant.getLong(TemporalField field) method
  
import java.time.*;
import java.time.temporal.ChronoField;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create a Instant object
        Instant instant
            = Instant.parse("2018-12-30T01:34:50.93Z");
  
        // get all enum of chronofield
        // and iterate through all enum values
        for (ChronoField field : ChronoField.values()) {
  
            try {
                // get long value of field
                long value = instant.getLong(field);
                System.out.println("field : " + field
                                   + " || value : " + value);
            }
            catch (Exception e) {
  
                System.out.println("field : " + field
                                   + " is not supported");
            }
        }
    }
}

输出：

field : NanoOfSecond || value : 930000000
field : NanoOfDay is not supported
field : MicroOfSecond || value : 930000
field : MicroOfDay is not supported
field : MilliOfSecond || value : 930
field : MilliOfDay is not supported
field : SecondOfMinute is not supported
field : SecondOfDay is not supported
field : MinuteOfHour is not supported
field : MinuteOfDay is not supported
field : HourOfAmPm is not supported
field : ClockHourOfAmPm is not supported
field : HourOfDay is not supported
field : ClockHourOfDay is not supported
field : AmPmOfDay is not supported
field : DayOfWeek is not supported
field : AlignedDayOfWeekInMonth is not supported
field : AlignedDayOfWeekInYear is not supported
field : DayOfMonth is not supported
field : DayOfYear is not supported
field : EpochDay is not supported
field : AlignedWeekOfMonth is not supported
field : AlignedWeekOfYear is not supported
field : MonthOfYear is not supported
field : ProlepticMonth is not supported
field : YearOfEra is not supported
field : Year is not supported
field : Era is not supported
field : InstantSeconds || value : 1546133690
field : OffsetSeconds is not supported

方案二：

// Java program to demonstrate
// Instant.getLong(TemporalField field) method
  
import java.time.*;
import java.time.temporal.ChronoField;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create a Instant object
        Instant instant
            = Instant.parse("2018-12-30T01:34:50.93Z");
  
        // get Instant second value from this Instant
        // using getLong method
        long secondvalue
            = instant.getLong(
                ChronoField.INSTANT_SECONDS);
  
        // print result
        System.out.println("Instant Seconds: "
                           + secondvalue);
    }
}

输出：

Instant Seconds: 1546133690

程序 3：获取 UnsupportedTemporalTypeException

// Java program to demonstrate
// Instant.getLong(TemporalField field) method
  
import java.time.*;
import java.time.temporal.ChronoField;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create a Instant object
        Instant instant
            = Instant.parse("2018-12-30T01:34:50.93Z");
  
        // try to find AMPM_OF_DAY
        // using ChronoField.AMPM_OF_DAY
        // in getLong method
        try {
  
            long secondvalue
                = instant.getLong(
                    ChronoField.AMPM_OF_DAY);
        }
        catch (Exception e) {
  
            // print exception
            System.out.println("Exception: " + e);
        }
    }
}

输出：

Exception:
 java.time.temporal.UnsupportedTemporalTypeException:
 Unsupported field: AmPmOfDay

参考资料：https: Java Java)