Question

I’m studying oracle tutorials and have a few questions regarding the chapter Using an “Interface as a Type” from here so I try to understand how to invoke the method findLargest.

I’ve tried to modify a bit source code to get the better understanding, but nothing helps 🙁

here is my code:

public class RectanglePlus implements Relatable {

    public int width = 0;
    public int height = 0;

    public RectanglePlus() {
    }

    public RectanglePlus(int w, int h) {
        width = w;
        height = h;
    }

    // a method for computing the area of the rectangle
    public int getArea() {
        return width * height;
    }

    // a method required to implement the Relatable interface

    public int isLargerThan(Relatable other) {
        RectanglePlus otherRect = (RectanglePlus) other;
        if (this.getArea() < otherRect.getArea()) {
            return -1;
        } else if (this.getArea() > otherRect.getArea()) {
            return 1;
        } else {
            return 0;
        }
    }

    // and here is the method that i cant invoke
    public RectanglePlus findLargest(RectanglePlus object1,
            RectanglePlus object2) {
        Relatable obj1 = (Relatable) object1;
        Relatable obj2 = (Relatable) object2;
        if ((obj1).isLargerThan(obj2) > 0) {
            return object1;
        } else {
            return object2;
        }
    }

    public static void main(String[] args) {
        RectanglePlus test1 = new RectanglePlus(10, 20);
        RectanglePlus test2 = new RectanglePlus(20, 20);
    }
}

So, how can I invoke findLarge method on order to compare test1 and test 2? (I know it doesn’t make sense to find the largest object since I know it from the method isLargerThan, but I just try to understand a principle)

Its not a static method so I cant just say “RectanglePlus.findLarger(test1, test2)”.

How I do that?

Answer 1

Because findLargest is not static, you can use any RectanglePlus to call the function:

test1.findLargest(test1,test2);

or

test2.findLargest(test1,test2);