Object Diagram

Before reading more about object diagrams, you might want to refresh your memory on what a class diagram is, since an object diagram is just a specific instance of a class diagram. Object diagrams can help non-technical thinkers to understand the layout of a structural diagram by using specific instances instead of more abstract classes.

What is an Object Diagram in UML?

A UML object diagram represents a specific instance of a class diagram at a certain moment in time. When represented graphically you'll see many similarities to the class diagram. We used the same Car class example from the class diagram page to illustrate object diagrams.

Object Diagram vs Class Diagram

object diagram
Object Diagram Example
object diagram vs class diagram
Class Diagram Example

An object diagram can also focus on the links between the instances if you're using more than one object at a time. For example, linking to different car instances is an example of an object diagram. The association between those two instances is a link. More often than not, though, you will be using class diagrams to describe objects.

Other UML Object Diagram Examples

The UML specifications don't really change when you're describing an objective diagram in different programming languages. The whole point of UML is so that you can plan out software independent of specific platforms. Below are the most commonly searched types of object diagram types in different programming languages.

Objective C Object Diagram

Objective C has become very popular since Apple's release of "Objective C 2.0", and now it's the programming language of choice for Apple marketplace applications. Someone searching for an Objective C object diagram is probably attempting to show instances for an iPhone app.

Java Object Diagram

This term needs a little disambiguation. There are object diagram that can be used in UML to describe instances that would ultimately be programmed in Java. There also exist diagrams which describe Java objects that have nothing to do with UML. Whether you are looking for the former or the latter, Lucidchart can help map the structure you need to create. Click here to try out our demo.

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