Package ai.timefold.solver.core.preview.api.domain.metamodel

Interface ElementPosition

All Known Subinterfaces:

PositionInList, UnassignedElement

@NullMarked
public sealed interface ElementPosition
permits PositionInList, UnassignedElement

A supertype for PositionInList and UnassignedElement.

PlanningListVariable.allowsUnassignedValues() allows for a value to not be part of any entity's list. This introduces null into user code, and makes it harder to reason about the code. Therefore, we introduce UnassignedElement to represent this null value, and user code must explicitly decide how to handle this case. This prevents accidental use of UnassignedElement in places where PositionInList is expected, catching this error as early as possible.

This package and all of its contents are part of the Move Streams API, which is under development and is only offered as a preview feature. There are no guarantees for backward compatibility; any class, method, or field may change or be removed without prior notice, although we will strive to avoid this as much as possible.

We encourage you to try the API and give us feedback on your experience with it, before we finalize the API. Please direct your feedback to Timefold Solver Github.

Method Summary

Modifier and Type	Method	Description
default PositionInList	ensureAssigned()	Returns PositionInList if this position is assigned, otherwise throws an exception.
PositionInList	ensureAssigned(Supplier<String> messageSupplier)	Returns PositionInList if this position is assigned, otherwise throws an exception.
static PositionInList	of(Object entity, int index)	Create a new instance of PositionInList.
static UnassignedElement	unassigned()	Returns a singleton instance of UnassignedElement.

Method Details

of

static PositionInList of(Object entity,
 int index)

Create a new instance of PositionInList. User code should never need to call this method.

Parameters:

entity - Entity whose PlanningListVariable contains the value.

index - 0 or higher

Returns:

never null

unassigned

static UnassignedElement unassigned()

Returns a singleton instance of UnassignedElement. User code should never need to call this method.

Returns:

never null

ensureAssigned

default PositionInList ensureAssigned()

Returns PositionInList if this position is assigned, otherwise throws an exception.

Returns:

Position of the value in an entity's PlanningListVariable.

Throws:

IllegalStateException - If this position is unassigned.

ensureAssigned

PositionInList ensureAssigned(Supplier<String> messageSupplier)

Returns PositionInList if this position is assigned, otherwise throws an exception.

Parameters:

messageSupplier - The message to give the exception.

Returns:

Position of the value in an entity's PlanningListVariable.

Throws:

IllegalStateException - If this position is unassigned.