[Java] need help detecting line intersection

[PrisonLove]

So I'm trying to use the even-odd parity rule to determine if a point lies inside a polygon. You draw a directed line from your point, and if there are an even number of line intersections, the point lies outside the polygon, if there is an odd number, the point is inside.

My code snipped looks like this so far:

public boolean insidePolygon(Point p) {
    :
    :
    :

    int count = 0;
    int numSides = edgeList.size();  //edgeList is an ArrayList<edges> object
    for (int i = 0; i < numSides; i++) {
        edge e = edgeList.get(i);
        if (intersect(ray, e))
            count++;
    }
    if (count%2 == 0) 
        return false;
    return true;
}

private boolean intersect(edge e1, edge e2) {
    //I have no idea what to put here!
    return false;
}

My problem is that I don't know how to detect if two line segments intersect. For all intents and purposes an edge object is a line segment. Each edge only contains two Point objects as fields and that's it. edgeList is an ArrayList of edges containing all the edges of my polygon.

So what do I need to put in the intersect() method?

 

[Dr Super Good]

This article referenced via wikipedia may help you.

There is a more efficent "Shamos–Hoey algorithm" apparently acording to wikipedia but I do not know it.