How to express dependency in a UML Class Diagram?

Question

I the following two classes:

class a {
    void foo(){
        b object= new b();
        object.baar();
    }
}
class b {
    void baar(){
    }
}

How to express class a using class b with Class Diagram (which arrow to use)?

Answer 1

You would need to put a dashed dependency line, which may be directional or not.

• If class b makes use of class a, the dependency line should be bidirectional (or directionless)
• If class b does not make use of class a (except possibly through callbacks not tied directly to a) make the dashed line directional from a to b.

Answer 2

Whenever one class has a reference/uses another, it is said to have a dependency on it. In your example, class a uses class b. Therefore class a has a dependency on class b. For that, you can use the UML dashed line with open arrow as described here.

This is a very general relationship.

One class depends on another if the independent class is a parameter variable or local variable of a method of the dependent class.

If your class a had an instance variable, you would use the association link instead.