Question

i have Segment class who contain 2 sections , each section contain 2 point the X and Y coordinate.

Point class has getX() and getX() method.

public class Segment
{
    private Point pointLeft;
    private Point pointRight;
}

i want to find the overlap (is there is) between 2 sections:

public double overlap (Segment other)
{

}

how can i find it (only the X axis overlap)

the 2 sections parallel to X axis (each section has the same Y)

Answer 1

My understanding of your question is that you first want to project both lines on the X-axis, and then find their intersection.

That is, you want the length of the greyed out section on the X axis in the image above.

You’ll want to do it in 4 parts, like this:

if (other.pointLeft.X <= pointLeft.X && other.pointRight.X >= pointRight.X)
    return pointRight.X - pointLeft.X;

if (pointLeft.X <= other.pointLeft.X && pointRight.X >= other.pointRight.X)
    return other.pointRight.X - other.pointLeft.X;

if (pointLeft.X <= other.pointLeft.X && pointRight.X <= other.pointRight.X)
    return pointRight.X - other.pointLeft.X;

if (pointLeft.X >= other.pointLeft.X && pointRight.X >= other.pointRight.X)
    return other.pointRight.X - pointLeft.X;

return 0;

Note, I’ve coded this in place, and haven’t had a chance to test it. But it should give you a basic idea of what needs to be done.