Package org.djunits.quantity.def

Class AbstractReference<R extends AbstractReference<R,A,Q>,A extends AbsQuantity<A,Q,R>,Q extends Quantity<Q>>

java.lang.Object

org.djunits.quantity.def.AbstractReference<R,A,Q>

Type Parameters:

R - the reference type itself

A - the absolute quantity type for generics instantiation

Q - the relative quantity type for the offset

All Implemented Interfaces:

Reference<R,A,Q>, org.djutils.base.Identifiable

Direct Known Subclasses:

Direction.Reference, Position.Reference, Temperature.Reference, Time.Reference

public abstract class AbstractReference<R extends AbstractReference<R,A,Q>,A extends AbsQuantity<A,Q,R>,Q extends Quantity<Q>>
extends Object
implements Reference<R,A,Q>

Reference contains information about the reference point or origin / zero point of an absolute quantity.

Copyright (c) 2025-2026 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See for project information https://djunits.org. The DJUNITS project is distributed under a three-clause BSD-style license.

Author:

Alexander Verbraeck

Field Summary

Fields

Modifier and Type	Field	Description
protected static final Map<Class<?>,Map<String,Reference<?,?,?>>>	REFERENCES	Master registry: per concrete Reference subclass we keep a map of id to reference.

Constructor Summary

Constructors

Constructor	Description
AbstractReference(String id, String name, Q offset, R offsetReference)	Define a new reference point for the absolute quantity.

Method Summary

Modifier and Type	Method	Description
static boolean	containsId(Class<?> referenceClass, String id)	Check existence of id in a specific Reference subclass.
boolean	equals(Object obj)
static <R extends Reference<R, ?, ?>> R	get(Class<R> referenceClass, String id)	Fetch a reference by class and id.
String	getId()
String	getName()	Return the description of this reference point.
Q	getOffset()	Return the offset w.r.t. the offset reference, or zero when the offset is not defined.
R	getOffsetReference()	Return the offset reference for the offset, or null when the offset reference is not defined.
Map<String,Reference<?,?,?>>	getReferenceMap()	Return a safe copy of the static reference map for this Reference subclass.
int	hashCode()
abstract A	instantiate(Q quantity)	Return a strongly typed absolute quantity belonging to this reference.
protected static Map<String,Reference<?,?,?>>	mapFor(Class<?> referenceClass)	Get or create the inner map for a specific Reference subclass.
static Map<String,Reference<?,?,?>>	snapshotMap(Class<?> referenceClass)	Return a safe copy (snapshot) of the registry for a Reference subclass.
String	toString()
boolean	unregister()	Instance-level unregister; removes this reference from the per-class registry.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Details

REFERENCES

protected static final Map<Class<?>,Map<String,Reference<?,?,?>>> REFERENCES

Master registry: per concrete Reference subclass we keep a map of id to reference. This prevents name collisions between different absolute quantities.

Constructor Details

AbstractReference

public AbstractReference(String id,
 String name,
 Q offset,
 R offsetReference)

Define a new reference point for the absolute quantity. Prevent duplicate registration of the same id within the same Reference subclass.

Parameters:

id - the id

name - the name or explanation

offset - the offset w.r.t. the offsetReference, should be ZERO when offsetReference is null

offsetReference - the reference to which the offset is relative, can be null

Throws:

IllegalArgumentException - if an id is already registered for this Reference subclass

Method Details

mapFor

protected static Map<String,Reference<?,?,?>> mapFor(Class<?> referenceClass)

Get or create the inner map for a specific Reference subclass.

Parameters:

referenceClass - the reference class to look up

Returns:

the existing or new reference map for the the Reference subclass

get

public static <R extends Reference<R,
?,
?>> R get(Class<R> referenceClass,
 String id)

Fetch a reference by class and id. Returns null when not found.

Type Parameters:

R - the reference subclass type

Parameters:

referenceClass - the concrete Reference subclass

id - the id

Returns:

the reference instance or null

containsId

public static boolean containsId(Class<?> referenceClass,
 String id)

Check existence of id in a specific Reference subclass.

Parameters:

referenceClass - the reference subclass to check

id - the id to check

Returns:

whether the id exists for the Reference subclass

snapshotMap

public static Map<String,Reference<?,?,?>> snapshotMap(Class<?> referenceClass)

Return a safe copy (snapshot) of the registry for a Reference subclass.

Parameters:

referenceClass - the reference subclass to retrieve

Returns:

a safe copy of the reference map

getReferenceMap

public Map<String,Reference<?,?,?>> getReferenceMap()

Return a safe copy of the static reference map for this Reference subclass.

Specified by:

getReferenceMap in interface Reference<R extends AbstractReference<R,A,Q>,A extends AbsQuantity<A,Q,R>,Q extends Quantity<Q>>

Returns:

a safe copy of the static reference map for this subclass

unregister

public boolean unregister()

Instance-level unregister; removes this reference from the per-class registry. Intended primarily for unit tests to clean up temporary references. Existing objects that hold a direct pointer to this instance continue to work.

Specified by:

unregister in interface Reference<R extends AbstractReference<R,A,Q>,A extends AbsQuantity<A,Q,R>,Q extends Quantity<Q>>

Returns:

true if this reference was removed from the registry; false if it was not present

instantiate

public abstract A instantiate(Q quantity)

Return a strongly typed absolute quantity belonging to this reference.

Specified by:

instantiate in interface Reference<R extends AbstractReference<R,A,Q>,A extends AbsQuantity<A,Q,R>,Q extends Quantity<Q>>

Parameters:

quantity - the relative quantity that indicates the 'distance' to this reference point

Returns:

a strongly typed absolute quantity belonging to this reference

getOffset

public Q getOffset()

Return the offset w.r.t. the offset reference, or zero when the offset is not defined.

Specified by:

getOffset in interface Reference<R extends AbstractReference<R,A,Q>,A extends AbsQuantity<A,Q,R>,Q extends Quantity<Q>>

Returns:

the offset expressed in the relative quantity

getOffsetReference

public R getOffsetReference()

Return the offset reference for the offset, or null when the offset reference is not defined.

Specified by:

getOffsetReference in interface Reference<R extends AbstractReference<R,A,Q>,A extends AbsQuantity<A,Q,R>,Q extends Quantity<Q>>

Returns:

the offset reference

getId

public String getId()

Specified by:

getId in interface org.djutils.base.Identifiable

getName

public String getName()

Description copied from interface: Reference

Return the description of this reference point.

Specified by:

getName in interface Reference<R extends AbstractReference<R,A,Q>,A extends AbsQuantity<A,Q,R>,Q extends Quantity<Q>>

Returns:

description of this reference point

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object