Class-level metrics

Coupling metrics for object-oriented languages

For a given class, these metrics count relationships where source or destination is presented by the class or by its methods/attributes.

All these relationships are divided into groups according to three factors.

1. Type of relationship between a given class and an interacting class: their relationship (whether it is a parent-child relationship or other);
2. Type of interaction (whether current class has an attribute, method parameter, or return type of another class, or class-method from one class invoke class-method from another class);
3. Focus of impact (whether a class is using another class through its attributes, methods or method types — import — or it is used by another class - export).

One should notice that all the names of the metrics are acronyms of the metric's description. First letters in the acronyms stand for these 3 types of interactions: A for ancestor, D for descendant, O for other (neither ancestor nor descendant), 2nd and 3rd letters encode interaction CA for class-attribute, CM for class-method, MM for method-method, IC for import coupling and EC for export coupling.

Coupling metrics in the Klocwork system-level Java reports

The Klocwork system-level Java reports use the sum of the coupling metrics to indicate relative connectedness of classes.

Used by (export) coupling is OCAEC+OMMEC+OCMEC for each class.

Uses (import) coupling is OCAIC+OCMIC+OMMIC for each class.

Example

----------A.java-------------
public class A extends B {
public C mal(int i) { C c = new C(); /*...*/return c; }
private B b1;
private D d1;
}
-----------------------------

----------B.java-------------
public class B extends D {
    public int mb1(D d) { int res = 0; /*....*/return res;}
    private C c1;
    private C c2;
}
-----------------------------

----------C.java-------------
public class C {
    public int mc1() { int res=k; /*...*/ return res;}
    private int k;
    private A a1;
    private A a2;
}
-----------------------------

----------D.java-------------
public class D {
    public void md1(int v) { }
}
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