How to put different color random dots in a rectangle separated by a diagonal (JAVA)

My problem is that I cant get the diagonal to resize properly. If I run the code the diagonal is on the wrong side and when I expand it vertically it doesn't maintain a perfect diagonal from one corner to another.

Below I have my code for the program and the driver. import javax.swing.JFrame;

public class Points
{

public static void main(String[] args)
{
  JFrame frame = new JFrame("Points");
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  PointsPanel panel = new PointsPanel();

  frame.getContentPane().add(panel);
  frame.pack();
  frame.setVisible(true);
  }
  }

Here is the main program

import javax.swing.JPanel;
import java.awt.Dimension;
import java.awt.Graphics;
import java.util.Random;
import java.awt.Color;
import java.lang.Math.*;

public class PointsPanel extends JPanel
{
 private final int MAX_POINTS = 20000;
 private final int LENGTH = 1;
 private int x,x1,y,y1;
 private Random random;
 double slope,b,c,g;


 public PointsPanel(){
  random = new Random();
  setBackground(Color.black);
  setPreferredSize(new Dimension(300,300));

 }


 public void paintComponent(Graphics page)
 {
  super.paintComponent(page);
 for(int count = 0; count < MAX_POINTS; count++)
 {

  x = random.nextInt(getWidth()-1) + 1;

  y = random.nextInt(getHeight()-1) + 1;

  x1= x + LENGTH;
  y1= y + LENGTH;

  slope = x1/y1;
    c = slope*x;
    b = ((-1)*(y))-c;
    g = (-1)*y1;

  if (b <= g)

     page.setColor(Color.red);
  else
     page.setColor(Color.green);
     page.drawLine(x,y,x1,y1);
 }
  }
 }