# Java Program to Find Area of a Polygon using Slicker Algorithm

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This is a Java Program to find the area of a polygon using slicker method. The algorithm assumes the usual mathematical convention that positive y points upwards. In computer systems where positive y is downwards (most of them) the easiest thing to do is list the vertices counter-clockwise using the “positive y down” coordinates. The two effects then cancel out to produce a positive area.

Here is the source code of the Java Program to Implement Slicker Algorithm that avoids Triangulation to Find Area of a Polygon. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

1. `//This is a java program to find the area of polygon using Slicker algorithm`
2. `import java.util.*;`
3. ` `
4. `class Area_polygon_Slicker`
5. `{`
6. `    static final int MAXPOLY = 200;`
7. `    static final double EPSILON = 0.000001;`
8. ` `
9. `    static class Point`
10. `    {`
11. `        double x, y;`
12. `    }`
13. ` `
14. `    static class Polygon`
15. `    {`
16. `        Point p[] = new Point[MAXPOLY];`
17. `        int n;`
18. ` `
19. `        Polygon()`
20. `        {`
21. `            for (int i = 0; i < MAXPOLY; i++)`
22. `                p[i] = new Point();`
23. `        }`
24. `    }`
25. ` `
26. `    static double area(Polygon p)`
27. `    {`
28. `        double total = 0;`
29. `        for (int i = 0; i < p.n; i++)`
30. `        {`
31. `            int j = (i + 1) % p.n;`
32. `            total += (p.p[i].x * p.p[j].y) - (p.p[j].x * p.p[i].y);`
33. `        }`
34. `        return total / 2;`
35. `    }`
36. ` `
37. `    static public void main(String[] args)`
38. `    {`
39. `        Polygon p = new Polygon();`
40. `        Scanner sc = new Scanner(System.in);`
41. `        System.out.println("Enter the number of points in Polygon: ");`
42. `        p.n = sc.nextInt();`
43. `        System.out.println("Enter the coordinates of each point: <x> <y>");`
44. `        for (int i = 0; i < p.n; i++)`
45. `        {`
46. `            p.p[i].x = sc.nextDouble();`
47. `            p.p[i].y = sc.nextDouble();`
48. `        }`
49. ` `
50. `        double area = area(p);`
51. `        if (area > 0)`
52. `            System.out.print("The Area of Polygon with " + p.n`
53. `                    + " points using Slicker Algorithm is : " + area);`
54. `        else`
55. `            System.out.print("The Area of Polygon with " + p.n`
56. `                    + " points using Slicker Algorithm is : " + (area * -1));`
57. `        sc.close();`
58. `    }`
59. `}`

Output:

```\$ javac Area_polygon_Slicker.java
\$ java Area_polygon_Slicker

Enter the number of points in Polygon:
4
Enter the coordinates of each point: <x> <y>
1 1
1 6
6 6
6 1
The Area of Polygon with 4 points using Slicker Algorithm is : 25.0

Enter the number of points in Polygon:
5
Enter the coordinates of each point: <x> <y>
1 2
4 5
9 8
3 2
1 5
The Area of Polygon with 5points using Slicker Algorithm is : 6.0```

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