s = A xt + B yt + C
If s < 0, t lies in the clockwise halfplane of L; if s > 0, t lies on the counter-clockwise halfplane; if s = 0, t lies on L.
For example, the equation of the line connecting points (2, 2) and (4, 5) is -3x + 2y + 2 = 0. The point (6, 3) lies in the clockwise halfplane of this line, because (-3)(6) + (2)(3) + 2 = -10. Conversely, the point (0, 5) lies in the other halfplane as (-3)(0) +(2)(5) +2 = 12.
Here is the source code of the Java Program to Apply Above-Below-on Test to Find the Position of a Point with respect to a Line. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.
//This is a java program to check whether a point lies on, above or below the gievn line
public class Position_Point_WRT_Line
public static void main(String args)
Random random = new Random();
int x1, x2, y1, y2;
x1 = random.nextInt(10);
x2 = random.nextInt(10);
y1 = random.nextInt(10);
y2 = random.nextInt(10);
System.out.println("The Equation of the line is : (" + (y2 - y1)
+ ")x+(" + (x1 - x2) + ")y+(" + (x2 * y1 - x1 * y2) + ") = 0");
System.out.println("Enter the point : <x>,<y>");
Scanner scan = new Scanner(System.in);
int x, y;
x = scan.nextInt();
y = scan.nextInt();
int s = (y2 - y1) * x + (x1 - x2) * y + (x2 * y1 - x1 * y2);
if (s < 0)
.println("The point lies below the line or left side of the line");
else if (s > 0)
.println("The point lies above the line or right side of the line");
System.out.println("The point lies on the line");
$ javac Position_Point_WRT_Line.java $ java Position_Point_WRT_Line The Equation of the line is : (-2)x+(-9)y+(81) = 0 Enter the point : <x>,<y> 2 3 The point lies above the line or right side of the line
Sanfoundry Global Education & Learning Series – 1000 Java Programs.