Question

Write a program that accepts (x1, y1) and (x2, y2) to specify line 1, (x3, y3) and (x4, y4) to specify line 2, computes and output the intersection of the two lines and the angle between them.

Answer 1

Code -

class xyPoint
{
   double x,y;
  
   public xyPoint(double x, double y)
   {
       this.x = x;
       this.y = y;
   }
   //this method return the x, y coordinate of the point
   static void diplayCoordinate(xyPoint p)
   {
       System.out.println("(" + p.x + ", " + p.y + ")");
   }
}

class Main
{     
   static xyPoint pointOfIntersection(xyPoint A, xyPoint B, xyPoint C, xyPoint D)
   {
//line A-B
       double a1 = B.y - A.y;
       double b1 = A.x - B.x;
       double c1 = a1*(A.x) + b1*(A.y);
  
       //LINE C-D
       double a2 = D.y - C.y;
       double b2 = C.x - D.x;
       double c2 = a2*(C.x)+ b2*(C.y);
  
       double detarminant = a1*b2 - a2*b1;
  
       if (detarminant == 0)
       {
           //line are parallel
           return new xyPoint(Double.MAX_VALUE, Double.MAX_VALUE);
       }
       else
       {
//return the intersection point
           double x = (b2*c1 - b1*c2)/detarminant;
           double y = (a1*c2 - a2*c1)/detarminant;
           return new xyPoint(x, y);
       }
   }
  
   static double angleBetweenLine(xyPoint A, xyPoint B, xyPoint C, xyPoint D) {
   double m1 = (B.y-A.y)/(B.x-A.x);
   double m2 = (D.y-C.y)/(D.x-C.x);
   double angle = (double) Math.toDegrees(Math.atan((m2-m1)/(1-(m1*m2))));
   if(angle < 0){
angle += 360;
}

return angle;
}
  
   public static void main(String args[])
   {
       xyPoint A = new xyPoint(1, 1);
       xyPoint B = new xyPoint(4, 4);
       xyPoint C = new xyPoint(1, 8);
       xyPoint D = new xyPoint(2, 4);
  
       xyPoint intersection = pointOfIntersection(A, B, C, D);
      
       double angle = angleBetweenLine(A, B, C, D);
       System.out.println("Angle between line "+angle+"degree");
  
//if the lines are parallel
       if (intersection.x == Double.MAX_VALUE &&
           intersection.y == Double.MAX_VALUE)
       {
           System.out.println("The given lines AB and CD are parallel.");
       }
//print the intersection point
       else
       {
       System.out.print("The intersection of the given lines AB " +
                           "and CD is: ");
       xyPoint.diplayCoordinate(intersection);
       }
   }
}

Screenshots -