UML Class Diagrams

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Index

1. Attributes
2. Methods
3. Visibility Notation
4. Classes Dependance

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UML Class Notation

The UML Class diagram is a graphical notation used to construct and visualise object oriented systems by showing the system’s:

1. Class Name:

   • The name of the class is typically written in the top compartment of the class box and is centred and bold.

2. Attributes

   • Attributes, also known as properties or fields, represent the data members of the class.
   • They are listed in the second compartment of the class box and often include the visibility (e.g. public, private) and the data type of each attribute.

3. Methods

   • Methods, also known as functions or operations, represent the behaviour or functionality of the class.
   • They are listed in the third compartment of the class box and include the visibility (e.g., public, private), return type, and parameters of each method.

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Attributes

In UML Class Diagram notation visibility fieldName : dataType <static> <final> is a way to represent the fields of a class.

Here’s what each part means:

• visibility: This indicates the visibility of the attribute. It can be public (+), private (-), protected (#), or package (~).

  • read Visibility Notation for more information

• fieldName: This is the name of the field.

• dataType: This is the type of the attribute (e.g., int, String, etc.).

• <static>: If present, this indicates that the attribute is static.

• <final>: If present, this indicates that the attribute is final.

For example, - count : int <static> <final> would represent a private, static, final attribute named count of type int.

Tip

Read about Java Fields to lear more

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Methods

In UML Class Diagram notation, methods are represented visibility methodName(parameters) : returnType <static> <abstract>

Here’s what each part means:

• visibility: This indicates the visibility of the method. It can be public (+), private (-), protected (#), or package (~).

  • read Visibility Notation for more information

• methodName: This is the name of the method.

• parameters: These are the input parameters for the method. Each parameter includes a name and a type, separated by a colon, and multiple parameters are separated by commas.

• returnType: This is the type of value that the method returns.

• <static>: If present, this indicates that the method is static. In UML, static methods are usually underlined.

For example, + calculateSum(a: int, b: int) : int <static> would represent a public, static method named calculateSum that takes two parameters of type int and returns an int.

Tip

Read about Java Methods to learn more

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Visibility Notation

Visibility notations indicate the access level of attributes and methods. Common visibility notations include:

• + for public (visible to all classes)
• - for private (visible only within the class)
• # for protected (visible to subclasses)
• ~ for package or default visibility (visible to classes in the same package)

Tip

Read Java Access Modifier to learn more

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Classes Dependance

Posso utilizzare la freccia piena in modo tale da indicare la dipendenza generica tra due classi.

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