How to get the difference in a point?

Question

So I recently was introduced to Points in my class. Right now I am trying to find the difference of X and then the difference of Y and then add them together. I am so lost and cant quite find the right answer. What are some options for this?

Just a heads up this is using the Point class.

Better put I dont understand the Point class that I was taught in my AP Computer Science class. Not that I don't understand how to subtract x2-x1. What command would I use to accomplish this because I continue to get errors when typing x2-x1.

Heres is what I am supposed to do: "In our case, the Manhattan distance is the sum of the absolute values of the differences in their coordinates; in other words, the difference in x plus the difference in y between the points." Exact words from teacher.

Answer 1

Difference of two X points? If so, you would do X1-X2...same with Y points... Y1-Y2.

To make sure the difference is positive, you can do

Math.abs(p.X1-p.X2)

likewise...

Math.abs(p.Y1-p.Y2)

then just add them together...

Math.abs(p.X1-p.X2) + Math.abs(p.Y1-p.Y2)

After your clarifications...I have revised my answer

public int manhattanDistance(Point other){ //not sure why return an int...I think returning a double makes more sense..
    int xdist = Math.abs(this.x-other.x);
    int ydist = Math.abs(this.y-other.y);
    return (int)xdist+ydist; //cast to int because you must return int

}

or less code version...

    public int manhattanDistance(Point other){
    return (int)Math.abs(this.x-other.x) + Math.abs(this.y-other.y);     
}

Answer 2

The distance between two points (in a straight line) can be calculated as:

   ___________________________
  /           2              2
 / (p2x - p1x)  + (p2y - p1y)
v

For example, the classic 3-4-5 triangle:

    4
  +---*
  |  /
3 | / 5
  |/
  *

The hypotenuse (5) can be calculated as the square root of 3 * 3 + 4 * 4.

One way you would do that with two Point objects in Java would be with:

dist = (point2.x - point1.x) * (point2.x - point1.x)
     + (point2.y - point1.y) * (point2.y - point1.y);

though you could also use Math.pow(something,2) in place of the multiplications.

---

If on the other hand you wanted to find the Manhattan distance (as now seems evident by the extra information added to the question), you would use something like:

mdist = Math.abs (point2.x - point1.x) + Math.abs (point2.y - point1.y);

This works out the X difference (which may be negative) then takes the absolute value of that to force it to positive. Then it does the same with the Y difference and adds them together.