Question

As far as I know an Is-a relation is where your class extends another class, i.e., A extends B therefore A is a B.

And a has-a relation is when a class implements an interface so A has an algoritm.

My question: is there ever a situation where an is-a is also a has-a?

or where implementing an interface can become a is-a relation?

let me rephase that:

can a class have an is-a relationship if it implements an interface?

Answer 1

And a has-a relation is when a class implements an interface so A has
a Aalgoritm.

This statement is wrong. if you implement an interface its still a Is-A relationship.

Has-A relationship (composition) is something like this:

Class ABC {
private XYZ z;
}

ABC has-a XYZ.