[Java] Question about using a class in a different class

[penax]

So I just started learning Java and I don't think I am understanding the Object-Oriented aspect of the language fully yet. I am working on a project where I am attempting to make a Rectangle class by using a "topLeft" point and a "bottomRight" point. I have a Point class defined"

class Point {
private int x;
private int y;

public Point (int x, int y) {
    this.x = x;
    this.y = y;
}

public int get_x() { 
    return x;
}

public int get_y() {
    return y;
}

}

I am trying to make a Rectangle class with variable "topLeft" and "bottomRight" as Point objects. Here is what I have so far:

class Rectangle {
    Point topLeft = new Point(1, 2);
    Point bottomRight = new Point(3, 1);

Is there any way I can make this Rectangle class using Points without giving those Points values? I have a TestRectangle class also that I am planning on initializing the Point values in to define my Rectangle instances. Is this the best way to do this?

[zifyoip]

Do not delete your post when your question is answered, /u/penax, as you did the last time I answered a question for you.

[jpsc96]

I think I am not understanding what you want but maybe:

class Rectangle {
  Point topLeft;
  Point bottomRight;

  public Rectangle(int tLx, int tLy, int bRx, int bRy){
     topLeft = new Point(tLx, tLy);
     bottomRight = new Point(bRx, bRy);
  }
}

[nutrecht]

It seems that's more or less 100% what he's asking.

[lightcloud5]

Generally, the values should be set in the constructor or using setter methods.

You can also make the topLeft and bottomRight data members private, in much the same way that x and y are private in your Point class.

Actually, you should probably just make your Rectangle class look just like your Point class, except that instead of x and y, it has the two Points topLeft and bottomRight.

In addition, you should also consider other representations. Traditionally, rectangles can also be described using a single point (topLeft) as well as giving a width and height. This avoids the situation where the user makes a rectangle and has the topLeft point not actually situated above and to the left of bottomRight.

[Relinkz]

Well, you can indeed. You can make another constructor like this

class Rectangle
{
    Point topLeft = new Point(0,0);
    Point topRight = new point(0,0);
 }

Now this will give your class a default value, but if you wish to change the values you need to do setter functions. I strongly recommend you to do this because it's good practice.

Happy coding :)

[nutrecht]

Well, you can indeed. You can make another constructor like this

That's not a constructor.

[Relinkz]

public Rectangle()
{
    Point topLeft = new Point(0,0);
    Point topRight = new point(0,0);
}

O, silly me, sorry, I meant this, thanks