Package java.time.chrono

Interface Era

  • All Superinterfaces:
    TemporalAccessor, TemporalAdjuster
    All Known Implementing Classes:
    IsoEra
    public interface Era
extends TemporalAccessor, TemporalAdjuster
    An era of the time-line.

    Most calendar systems have a single epoch dividing the time-line into two eras. However, some calendar systems, have multiple eras, such as one for the reign of each leader. In all cases, the era is conceptually the largest division of the time-line. Each chronology defines the Era's that are known Eras and a Chronology.eras to get the valid eras.

    For example, the Thai Buddhist calendar system divides time into two eras, before and after a single date. By contrast, the Japanese calendar system has one era for the reign of each Emperor.

    Instances of Era may be compared using the == operator.

    This interface must be implemented with care to ensure other classes operate correctly. All implementations must be singletons - final, immutable and thread-safe. It is recommended to use an enum whenever possible.

    • Method Detail

      • getValue

        int getValue()
        Gets the numeric value associated with the era as defined by the chronology. Each chronology defines the predefined Eras and methods to list the Eras of the chronology.

        All fields, including eras, have an associated numeric value. The meaning of the numeric value for era is determined by the chronology according to these principles:

        • The era in use at the epoch 1970-01-01 (ISO) has the value 1.
        • Later eras have sequentially higher values.
        • Earlier eras have sequentially lower values, which may be negative.
        Returns:
        the numeric era value

      • isSupported

        boolean isSupported​(@Nullable
                    TemporalField field)
        Checks if the specified field is supported.

        This checks if this era can be queried for the specified field. If false, then calling the range and get methods will throw an exception.

        If the field is a ChronoField then the query is implemented here. The ERA field returns true. All other ChronoField instances will return false.

        If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.isSupportedBy(TemporalAccessor) passing this as the argument. Whether the field is supported is determined by the field.

        Specified by:
        isSupported in interface TemporalAccessor
        Parameters:
        field - the field to check, null returns false
        Returns:
        true if the field is supported on this era, false if not

      • range

        ValueRange range​(TemporalField field)
        Gets the range of valid values for the specified field.

        The range object expresses the minimum and maximum valid values for a field. This era is used to enhance the accuracy of the returned range. If it is not possible to return the range, because the field is not supported or for some other reason, an exception is thrown.

        If the field is a ChronoField then the query is implemented here. The ERA field returns the range. All other ChronoField instances will throw an UnsupportedTemporalTypeException.

        If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.rangeRefinedBy(TemporalAccessor) passing this as the argument. Whether the range can be obtained is determined by the field.

        The default implementation must return a range for ERA from zero to one, suitable for two era calendar systems such as ISO.

        Specified by:
        range in interface TemporalAccessor
        Parameters:
        field - the field to query the range for, not null
        Returns:
        the range of valid values for the field, not null
        Throws:
        DateTimeException - if the range for the field cannot be obtained
        UnsupportedTemporalTypeException - if the unit is not supported

      • get

        int get​(TemporalField field)
        Gets the value of the specified field from this era as an int.

        This queries this era for the value of the specified field. The returned value will always be within the valid range of values for the field. If it is not possible to return the value, because the field is not supported or for some other reason, an exception is thrown.

        If the field is a ChronoField then the query is implemented here. The ERA field returns the value of the era. All other ChronoField instances will throw an UnsupportedTemporalTypeException.

        If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.getFrom(TemporalAccessor) passing this as the argument. Whether the value can be obtained, and what the value represents, is determined by the field.

        Specified by:
        get in interface TemporalAccessor
        Parameters:
        field - the field to get, not null
        Returns:
        the value for the field
        Throws:
        DateTimeException - if a value for the field cannot be obtained or the value is outside the range of valid values for the field
        UnsupportedTemporalTypeException - if the field is not supported or the range of values exceeds an int

      • getLong

        long getLong​(TemporalField field)
        Gets the value of the specified field from this era as a long.

        This queries this era for the value of the specified field. If it is not possible to return the value, because the field is not supported or for some other reason, an exception is thrown.

        If the field is a ChronoField then the query is implemented here. The ERA field returns the value of the era. All other ChronoField instances will throw an UnsupportedTemporalTypeException.

        If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.getFrom(TemporalAccessor) passing this as the argument. Whether the value can be obtained, and what the value represents, is determined by the field.

        Specified by:
        getLong in interface TemporalAccessor
        Parameters:
        field - the field to get, not null
        Returns:
        the value for the field
        Throws:
        DateTimeException - if a value for the field cannot be obtained
        UnsupportedTemporalTypeException - if the field is not supported

      • adjustInto

        Temporal adjustInto​(Temporal temporal)
        Adjusts the specified temporal object to have the same era as this object.

        This returns a temporal object of the same observable type as the input with the era changed to be the same as this.

        The adjustment is equivalent to using Temporal.with(TemporalField, long) passing ChronoField.ERA as the field.

        In most cases, it is clearer to reverse the calling pattern by using Temporal.with(TemporalAdjuster): 

           // these two lines are equivalent, but the second approach is recommended
   temporal = thisEra.adjustInto(temporal);
   temporal = temporal.with(thisEra);

        This instance is immutable and unaffected by this method call.

        Specified by:
        adjustInto in interface TemporalAdjuster
        Parameters:
        temporal - the target object to be adjusted, not null
        Returns:
        the adjusted object, not null
        Throws:
        DateTimeException - if unable to make the adjustment