ValueConvertable (groovy 2.5.15 API)

To support caches whose values are convertable, e.g. SoftReference, WeakReference
Parameters:
- source value type, e.g. SoftReference, WeakReference
- target value type, e.g. value that SoftReference or WeakReference referenced

Methods
Type Params	Return Type	Name and description
	`V2`	`convertValue(V1 value)` convert the original value to the target value

[Java] Interface ValueConvertable<V1, V2>