VariableListener (OptaPlanner Javadoc 8.30.0.Final API)

Type Parameters:

Solution_ - the solution type, the class with the PlanningSolution annotation

Entity_ -

All Superinterfaces:

AbstractVariableListener<Solution_,Entity_>, AutoCloseable, Closeable

All Known Subinterfaces:

CustomShadowVariable.NullVariableListener

All Known Implementing Classes:

AnchorVariableListener, CollectionInverseVariableListener, ExternalizedAnchorVariableSupply, ExternalizedCollectionInverseVariableSupply, ExternalizedSingletonInverseVariableSupply, SingletonInverseVariableListener
```
public interface VariableListener<Solution_,Entity_>
extends AbstractVariableListener<Solution_,Entity_>
```
A listener sourced on a basic PlanningVariable.
Changes shadow variables when a source basic planning variable changes. The source variable can be either a genuine or a shadow variable.
Important: it must only change the shadow variable(s) for which it's configured! It should never change a genuine variable or a problem fact. It can change its shadow variable(s) on multiple entity instances (for example: an arrivalTime change affects all trailing entities too).
It is recommended to keep implementations stateless. If state must be implemented, implementations may need to override the default methods (AbstractVariableListener.resetWorkingSolution(ScoreDirector), AbstractVariableListener.close()).

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	Description
`void`	`afterVariableChanged(ScoreDirector<Solution_> scoreDirector, Entity_ entity)`
`void`	`beforeVariableChanged(ScoreDirector<Solution_> scoreDirector, Entity_ entity)`
`default boolean`	`requiresUniqueEntityEvents()`	When set to `true`, this has a performance loss.

Methods inherited from interface org.optaplanner.core.api.domain.variable.AbstractVariableListener
afterEntityAdded, afterEntityRemoved, beforeEntityAdded, beforeEntityRemoved, close, resetWorkingSolution

- Method Detail
  - requiresUniqueEntityEvents
```
default boolean requiresUniqueEntityEvents()
```
    When set to true, this has a performance loss. When set to false, it's easier to make the listener implementation correct and fast.
    
    Returns:
    
    true to guarantee that each of the before/after methods is only called once per entity instance per operation type (add, change or remove).
  - beforeVariableChanged
```
void beforeVariableChanged(ScoreDirector<Solution_> scoreDirector,
                           Entity_ entity)
```
    Parameters:
    
    scoreDirector - never null
    
    entity - never null
  - afterVariableChanged
```
void afterVariableChanged(ScoreDirector<Solution_> scoreDirector,
                          Entity_ entity)
```
    Parameters:
    
    scoreDirector - never null
    
    entity - never null