# TemporalQuery

public interface **TemporalQuery** Strategy for querying a temporal object.


Queries are a key tool for extracting information from temporal objects.
They exist to externalize the process of querying, permitting different
approaches, as per the strategy design pattern.
Examples might be a query that checks if the date is the day before February 29th
in a leap year, or calculates the number of days to your next birthday.


The `https://developers.google.com/j2objc/javadoc/jre/reference/java/time/temporal/TemporalField.html` interface provides another mechanism for querying
temporal objects. That interface is limited to returning a `long`.
By contrast, queries can return any type.


There are two equivalent ways of using a `TemporalQuery`.
The first is to invoke the method on this interface directly.
The second is to use `https://developers.google.com/j2objc/javadoc/jre/reference/java/time/temporal/TemporalAccessor.html#query(java.time.temporal.TemporalQuery<R>)`:

```
   // these two lines are equivalent, but the second approach is recommended
   temporal = thisQuery.queryFrom(temporal);
   temporal = temporal.query(thisQuery);
 
```
It is recommended to use the second approach, `query(TemporalQuery)`, as it is a lot clearer to read in code.


The most common implementations are method references, such as
`LocalDate::from` and `ZoneId::from`.
Additional common queries are provided as static methods in `https://developers.google.com/j2objc/javadoc/jre/reference/java/time/temporal/TemporalQueries.html`.

### Public Method Summary

|---|---|
| abstract R | [queryFrom](https://developers.google.com/j2objc/javadoc/jre/reference/java/time/temporal/TemporalQuery.html#queryFrom(java.time.temporal.TemporalAccessor))([TemporalAccessor](https://developers.google.com/j2objc/javadoc/jre/reference/java/time/temporal/TemporalAccessor.html) temporal) Queries the specified temporal object. |

## Public Methods

#### public abstract R
**queryFrom**
([TemporalAccessor](https://developers.google.com/j2objc/javadoc/jre/reference/java/time/temporal/TemporalAccessor.html) temporal)

Queries the specified temporal object.


This queries the specified temporal object to return an object using the logic
encapsulated in the implementing class.
Examples might be a query that checks if the date is the day before February 29th
in a leap year, or calculates the number of days to your next birthday.


There are two equivalent ways of using this method.
The first is to invoke this method directly.
The second is to use `https://developers.google.com/j2objc/javadoc/jre/reference/java/time/temporal/TemporalAccessor.html#query(java.time.temporal.TemporalQuery<R>)`:

```
   // these two lines are equivalent, but the second approach is recommended
   temporal = thisQuery.queryFrom(temporal);
   temporal = temporal.query(thisQuery);
 
```
It is recommended to use the second approach, `query(TemporalQuery)`, as it is a lot clearer to read in code.

<br />

##### Parameters

| temporal | the temporal object to query, not null |
|---|---|

##### Returns

- the queried value, may return null to indicate not found

##### Throws

| [DateTimeException](https://developers.google.com/j2objc/javadoc/jre/reference/java/time/DateTimeException.html) | if unable to query |
| [ArithmeticException](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/ArithmeticException.html) | if numeric overflow occurs |
|---|---|