LongValuesSource (Lucene 6.5.0 API)

```
public abstract class LongValuesSource
extends Object
```
Base class for producing LongValues To obtain a LongValues object for a leaf reader, clients should call getValues(LeafReaderContext, DoubleValues). LongValuesSource objects for long and int-valued NumericDocValues fields can be obtained by calling fromLongField(String) and fromIntField(String). To obtain a LongValuesSource from a float or double-valued NumericDocValues field, use DoubleValuesSource.fromFloatField(String) or DoubleValuesSource.fromDoubleField(String) and then call DoubleValuesSource.toLongValuesSource().

Constructors
Constructor and Description
`LongValuesSource()`

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`static LongValuesSource`	`constant(long value)` Creates a LongValuesSource that always returns a constant value
`static LongValuesSource`	`fromIntField(String field)` Creates a LongValuesSource that wraps an int-valued field
`static LongValuesSource`	`fromLongField(String field)` Creates a LongValuesSource that wraps a long-valued field
`SortField`	`getSortField(boolean reverse)` Create a sort field based on the value of this producer
`abstract LongValues`	`getValues(LeafReaderContext ctx, DoubleValues scores)` Returns a `LongValues` instance for the passed-in LeafReaderContext and scores If scores are not needed to calculate the values (ie `returns false`, callers may safely pass `null` for the `scores` parameter.
`abstract boolean`	`needsScores()` Return true if document scores are needed to calculate values

Class LongValuesSource