Essence (Delta 1.2 API)

Type Parameters:

T - the type of dataset item

U - the distilled type for equivalence comparisons

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
public interface Essence<T,U>
```
A function to distill an item down to its essential features for equivalence comparisons. Implementations will typically return a copy of the item with fields defaulted where they are inessential for comparisons.

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	Description
`default Equivalence<T>`	`asEquivalence()`	Returns an `Equivalence` function derived from this instance, using default equivalence for the distilled items.
`default Equivalence<T>`	`asEquivalence(Equivalence<U> essenceEquivalence)`	Returns an `Equivalence` function derived from this instance.
`U`	`distill(T value)`	Return a distilled item for equivalence comparisons.

- Method Detail
  - distill
```
U distill(T value)
```
    Return a distilled item for equivalence comparisons.
    
    Parameters:
    
    value - the item to distill
    
    Returns:
    
    a distilled item for equivalence comparisons
  - asEquivalence
```
default Equivalence<T> asEquivalence()
```
    Returns an Equivalence function derived from this instance, using default equivalence for the distilled items.
    
    Returns:
    
    an Equivalence function derived from this instance
  - asEquivalence
```
default Equivalence<T> asEquivalence(Equivalence<U> essenceEquivalence)
```
    Returns an Equivalence function derived from this instance.
    
    Parameters:
    
    essenceEquivalence - an Equivalence function used to compare the distilled items
    
    Returns:
    
    an Equivalence function derived from this instance