UML Class Diagrams

Question

I'm new to UML and trying to get my head around Class diagrams. For example see the following diagram(assume scope is public):

Can class 1 directly access any of the methods and attributes below in other classes or can it only access its own methods and attributes? Similarly can for example class 2 access the methods and attributes in class 1?

The main reason I ask is I need to produce a report operation, which calculates the days income and the income would be calculated by having to iterate through classes and totaling then returning the value.

Many thanks

Answer 1

See http://www.objectmentor.com/resources/articles/umlClassDiagrams.pdf, paragraph Composition Relationships.

It says:

In UML relationships are presumed to be bidirectional unless the arrowhead is
present to restrict them.

Meaning since there is an arrow in your example only class2 is accessible by class1 and not the other way around.

Answer 2

You are showing a one-way association between Class 1 and Class 2 and a generalization of Class 2 to Class 3, 4 and 5. In this case, Class 1 can see all of the public attributes and methods of Class 2. It will also be able to see those same attributes and methods of Class 3, 4, and 5. However, it is not shown to have visibility to any extended attributes and methods of Class 3, 4 and 5. Also, Class 2 does not have visibility to Class 1 attributes or methods due to the one-way relationship.

Keep in mind that what is shown in UML is not a strict depiction of how visibility will work in implementation. You are showing the important relationships in UML. For instance, even though you are not showing the visibility of Class 1 to Class 2, in all likelihood, your implementation of Class 2 will be able to see all public members of Class 1.