UML Association vs Aggregation vs Composition - Javatpoint

Aggregation is a subset of association, is a collection of different things. It represents has a relationship. It is more specific than an association. It ... ⇧SCROLLTOTOP Home Java UML Pandas Python Java SQL Android Cloud JavaScript Servlet JSP Struts2 Spring Quiz Projects InterviewQ Comment Forum Training UMLTutorial UMLTutorial UMLBuildingBlocks UMLArchitecture UMLDiagrams UMLRelationship AssociationvsAggregationvsComposition UMLAssociation UMLDependency UMLGeneralization UMLRealization UMLClassDiagram UMLObjectDiagram UMLComponentDiagram UMLDeploymentDiagram UMLInteractionDiagram UMLUseCaseDiagram UMLSequenceDiagram UMLCollaborationDiagram UMLStateMachineDiagram UMLActivityDiagram UMLTimingDiagram UMLTools next→ ←prev UMLAssociationvs.Aggregationvs.Composition InUMLdiagrams,relationshipsareusedtolinkseveralthings.Itisaconnectionbetweenstructural,behavioral,orgroupingthings.FollowingarethestandardUMLrelationshipsenlistedbelow: Association Dependency Generalization Realization Association Associationrelationshipisastructuralrelationshipinwhichdifferentobjectsarelinkedwithinthesystem.Itexhibitsabinaryrelationshipbetweentheobjectsrepresentinganactivity.Itdepictstherelationshipbetweenobjects,suchasateacher,canbeassociatedwithmultipleteachers. Itisrepresentedbyalinebetweentheclassesfollowedbyanarrowthatnavigatesthedirection,andwhenthearrowisonbothsides,itisthencalledabidirectionalassociation.Wecanspecifythemultiplicityofanassociationbyaddingtheadornmentsonthelinethatwilldenotetheassociation. Example: 1)Asingleteacherhasmultiplestudents. 2)Asinglestudentcanassociatewithmanyteachers. Thecompositionandaggregationaretwosubsetsofassociation.Inbothofthecases,theobjectofoneclassisownedbytheobjectofanotherclass;theonlydifferenceisthatincomposition,thechilddoesnotexistindependentlyofitsparent,whereasinaggregation,thechildisnotdependentonitsparenti.e.,standalone.Anaggregationisaspecialformofassociation,andcompositionisthespecialformofaggregation. Aggregation Aggregationisasubsetofassociation,isacollectionofdifferentthings.Itrepresentshasarelationship.Itismorespecificthananassociation.Itdescribesapart-wholeorpart-ofrelationship.Itisabinaryassociation,i.e.,itonlyinvolvestwoclasses.Itisakindofrelationshipinwhichthechildisindependentofitsparent. Forexample: Hereweareconsideringacarandawheelexample.Acarcannotmovewithoutawheel.Butthewheelcanbeindependentlyusedwiththebike,scooter,cycle,oranyothervehicle.Thewheelobjectcanexistwithoutthecarobject,whichprovestobeanaggregationrelationship. Composition Thecompositionisapartofaggregation,anditportraysthewhole-partrelationship.Itdepictsdependencybetweenacomposite(parent)anditsparts(children),whichmeansthatifthecompositeisdiscarded,sowillitspartsgetdeleted.Itexistsbetweensimilarobjects. Asyoucanseefromtheexamplegivenbelow,thecompositionassociationrelationshipconnectsthePersonclasswithBrainclass,Heartclass,andLegsclass.Ifthepersonisdestroyed,thebrain,heart,andlegswillalsogetdiscarded. Associationvs.Aggregationvs.Composition Association Aggregation Composition Associationrelationshipisrepresentedusinganarrow. Aggregationrelationshipisrepresentedbyastraightlinewithanemptydiamondatoneend. Thecompositionrelationshipisrepresentedbyastraightlinewithablackdiamondatoneend. InUML,itcanexistbetweentwoormoreclasses. Itisapartoftheassociationrelationship. Itisapartoftheaggregationrelationship. Itincorporatesone-to-one,one-to-many,many-to-one,andmany-to-manyassociationbetweentheclasses. Itexhibitsakindofweakrelationship. Itexhibitsastrongtypeofrelationship. Itcanassociateonemoreobjectstogether. Inanaggregationrelationship,theassociatedobjectsexistindependentlywithinthescopeofthesystem. Inacompositionrelationship,theassociatedobjectscannotexistindependentlywithinthescopeofthesystem. Inthis,objectsarelinkedtogether. Inthis,thelinkedobjectsareindependentofeachother. Herethelinkedobjectsaredependentoneachother. Itmayormaynotaffecttheotherassociatedelementifoneelementisdeleted. Deletingoneelementintheaggregationrelationshipdoesnotaffectotherassociatedelements. Itaffectstheotherelementifoneofitsassociatedelementisdeleted. Example:Atutorcanassociatewithmultiplestudents,oronestudentcanassociatewithmultipleteachers. Example:Acarneedsawheelforitsproperfunctioning,butitmaynotrequirethesamewheel.Itmayfunctionwithanotherwheelaswell. Example:Ifafileisplacedinafolderandthatisfolderisdeleted.Thefileresidinginsidethatfolderwillalsogetdeletedatthetimeoffolderdeletion. 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