Exemplar (OpenTelemetry SDK Metrics)

All Known Implementing Classes:

DoubleExemplar, LongExemplar
```
@Immutable
public interface Exemplar
```
A sample input measurement.
Exemplars also hold information about the environment when the measurement was recorded, for example the span and trace ID of the active span when the exemplar was recorded.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`long`	`getEpochNanos()`	Returns the timestamp in nanos when measurement was collected.
`io.opentelemetry.api.common.Attributes`	`getFilteredAttributes()`	The set of key/value pairs that were filtered out by the aggregator, but recorded alongside the original measurement.
`String`	`getSpanId()`	(Optional) Span ID of the exemplar trace.
`String`	`getTraceId()`	(Optional) Trace ID of the exemplar trace.
`double`	`getValueAsDouble()`	Coerces this exemplar to a double value.

- Method Detail
  - getFilteredAttributes
```
io.opentelemetry.api.common.Attributes getFilteredAttributes()
```
    The set of key/value pairs that were filtered out by the aggregator, but recorded alongside the original measurement. Only key/value pairs that were filtered out by the aggregator should be included
  - getEpochNanos
```
long getEpochNanos()
```
    Returns the timestamp in nanos when measurement was collected.
  - getSpanId
```
@Nullable
String getSpanId()
```
    (Optional) Span ID of the exemplar trace.
    Span ID may be null if the measurement is not recorded inside a trace or the trace was not sampled.
  - getTraceId
```
@Nullable
String getTraceId()
```
    (Optional) Trace ID of the exemplar trace.
    Trace ID may be null if the measurement is not recorded inside a trace or if the trace is not sampled.
  - getValueAsDouble
```
double getValueAsDouble()
```
    Coerces this exemplar to a double value.
    Note: This could createa a loss of precision from long measurements.