cartesian slope calculation error Java

Question

I'm having some trouble with the my cartesian slope calculations in Java. So my sourcecode lets you input 4 numbers, x1 y1 x2 y2, which represent 2 coordinates of 2 points in an cartesian coordinate system.

then i calculate the slope by calculating deltaX and deltaY. so i use a double for the slope end calculation (deltaY / deltaX) in case you get a tenth of a number.

then i use an IF function to say: if slope = 0 --> println("not a linear line"). else calculate the cross point of the X and Y polars and println the result

So here is the problem: what if the slope is 0 (example x1:0 y1:1 x2:0 y2:9) then the i get an error: Exception in thread main java.lang.ArithmeticException: / by zero

here is the full script:

import java.io.*;

public class Cartesian
{
    public static int leesIn(String var, BufferedReader in) throws IOException
    {
        System.out.println("type een getal in die " + var + " moet voorstellen.");
        return Integer.parseInt(in.readLine());
    }
    public static void main(String[] args) throws IOException
    {


    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));

    int x1, x2, y1, y2;
    x1 = leesIn("X1", in);
    y1 = leesIn("Y1", in);
    x2 = leesIn("X2", in);
    y2 = leesIn("Y2", in);

    System.out.println("The Coördinates of point 1 is: (" + x1 + ", " + y1 + "). The Coördinates of point 2 is: (" + x2 + ", " + y2 + ").");


    int deltaY = y2 - y1;
    int deltaX = x2 - x1;
    double RC = deltaY / deltaX;

    if ((RC) == 0)
    {
        System.out.println("The slope is 0, no linear line.");
    }else
    {
        System.out.println("The slope is: " + RC);
        double B = y1-(RC*x1);
        System.out.println("The crosspoint with Y, if x is 0, : " + B);
    }
}
}

anyone an idea how to fix my problem? tnx in advance!

Answer 1

You should move calculation into area where you are sure that it can be calculated (in your case double RC = deltaY / deltaX;

So your code will be:

int deltaY = y2 - y1;
int deltaX = x2 - x1;

if (deltaY == 0)
{
    System.out.println("The slope is 0, no linear line.");
}else if (deltaX == 0)
{
    System.out.println("Not a Linear Line");
}else
{
    double RC = (double) deltaY / deltaX;
    System.out.println("The slope is: " + RC);
    double B = y1-(RC*x1);
    System.out.println("The crosspoint with Y, if x is 0, : " + B);
}

Answer 2

Make a try catch block

double RC;
try{
  RC = deltaY / deltaX;

}

catch(ArithmeticException ex){
System.out.println("Not a Linear Line");

}

Answer 3

try this

try {

  double RC = deltaY / deltaX;

  if ((RC) == 0)
  {
    System.out.println("The slope is 0, no linear line.");
  }else
  {
    System.out.println("The slope is: " + RC);
    double B = y1-(RC*x1);
    System.out.println("The crosspoint with Y, if x is 0, : " + B);
  }
} catch(ArithmeticException ae) {
    System.out.println("Not a linear line");
}