Coupling and dependencies clarification

Question

I'm currently learning about coupling and dependencies in Java. I've been reading this tutorial and understand that if class1 contains an instance of class2 and if you call a method like exampleMethod(c2), this counts as dependency between class1 and class2. However, I am unsure about the examples below. Can anyone give me some clarification?

Assuming that we are inside class1 (which contains class2 c2):

1. If class1 calls a method defined in class2 (c2.aMethod() for example), does this count as a dependency/coupling between class1 and class2?

2. Does calling c2.someSetterMethod(argument) count as dependency/coupling between class1 and class2?

3. Does calling c2.repaint() within class1 count as a dependency?

Answer 1

The fact that class1 contains a reference to an instance of class2 suffices to say that class1 depends on class2. In all of your 3 examples you need a reference to class2 in order to call its methods. This only increases the need for dependency in your class1 but not the dependency itself.

Please read http://depfind.sourceforge.net/Manual.html#Dependencies as mentioned in my answer to your previous question: https://stackoverflow.com/a/21689495/1659599.

Answer 2

1. Yes.
2. Yes.
3. Yes.

One way to reduce coupling is to use interfaces. This way, class 1 only knows about the interface, and is not coupled with class 2 specifically. And in fact, any class that implements the interface could be used instead of class 2 and class 1 would still be satisfied.