IndexShadowVariable (OptaPlanner Javadoc 8.30.0.Final API)

```
@Target({METHOD,FIELD})
@Retention(RUNTIME)
public @interface IndexShadowVariable
```
Specifies that a bean property (or a field) is an index of this planning value in another entity's PlanningListVariable.
It is specified on a getter of a java bean property (or a field) of a PlanningEntity class.
The source variable must be a list variable.

- Required Element Summary
  
  Required Elements
  Modifier and Type Required Element Description
  
  String sourceVariableName
  The source variable must be a list variable.

- Element Detail
  - sourceVariableName
```
String sourceVariableName
```
    The source variable must be a list variable.
    When the Solver changes a genuine variable, it adjusts the shadow variable accordingly. In practice, the Solver ignores shadow variables (except for consistency housekeeping).
    
    Returns:
    
    property name of the list variable that contains instances of this planning value