//package classes;

public class Line {
    
    Point point1;
    Point point2;
    
   // initialize the line class with the constructor
    public Line(Point Point1, Point point2) {
        this.point1 = Point1;
        this.point2 = point2;
    }
    
   // initialize the line class by passing the points
    public Line(int x1,int y1,int x2,int y2) {
        
        this.point1 = new Point(x1,y1);
        this.point2 = new Point(x2,y2);
    }
    
     public Point getPoint1() {
            return point1;
        }
        
        public Point getPoint2() {
            return point2;
        }
    
    // override the tostring to print the points
    public String toString() {
        return "[" +point1.toString()+", " +point2.toString()+"]";
    }
     
    //this method return the slope of two points
    public double getSlope() {
        if(point1.getX() == point2.getX())
            throw new IllegalArgumentException();
            
        double slope = (double) (point2.getY() - point1.getY()) / (point2.getX() - point1.getX());
        return slope;
    }


    public static void main(String[] args) {
        
        Line line = new Line(3,2,9,8);
        
        System.out.println("the string representation of the line is :"+line);
        System.out.println("slope of the line is: " +line.getSlope());
        
    }

}

Output:

the string representation of the line is :[(3,2), (9,8)]
slope of the line is: 1.0