UML Design class diagram: Class with another class as attribute

I'm having a pretty hard time trying to figure out how to model a certain scenario as a UML design class diagram.

Suppose I have the following situation:

I have a class named CPoint that has two attributes: x and y (coordinates in a R2 plane). Additionally, I have a class named CLine that should have two CPoint as attributes.

This is pretty straight forward to code (I'll use C++ in my example):

class CPoint{
    float x;
    float y;
    //Constructor, gets and sets here
}

And for CLine:

class CLine{
    CPoint p1;
    CPoint p2;
    //Constructor, gets and sets here
}

Now my question is: How do I model such a thing in UML?

I thought of something similar to this:

But then I was told that this is violating the principles of object oriented modeling, so then I did this:

But it does not convince me at all. Additionally, I was reading about design patterns and came to this UML design while reading about singletons:

Which makes me think my initial approach was just right. Additionally, I'm able to see that my first approach is just alright if I think about it as a C++ program. In Java, however, I'd still have to create the object by doing new CPoint(0, 0) in the CLine's constructor. I'm really confused about this.

So, how do I model this situation? Am I perhaps being too concrete when I attempt to model the situation?

Thanks in advance! This isn't letting me sleep at night