Basic Java Programs

Calculate Circle Area

1. import java.io.BufferedReader;
2. import java.io.IOException;
3. import java.io.InputStreamReader;
5. public class CalculateCircleAreaExample {
7. public static void main(String[] args) {
9. int radius = 0;
10. System.out.println("Please enter radius of a circle");
12. try
13. {
14. //get the radius from console
15. BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
16. radius = Integer.parseInt(br.readLine());
17. }
18. //if invalid value was entered
19. catch(NumberFormatException ne)
20. {
21. System.out.println("Invalid radius value" + ne);
22. System.exit(0);
23. }
24. catch(IOException ioe)
25. {
26. System.out.println("IO Error :" + ioe);
27. System.exit(0);
28. }
30. /*
31. * Area of a circle is
32. * pi * r * r
33. * where r is a radius of a circle.
34. */
36. //NOTE : use Math.PI constant to get value of pi
37. double area = Math.PI * radius * radius;
39. System.out.println("Area of a circle is " + area);
40. }
41. }
43. /*
44. Output of Calculate Circle Area using Java Example would be
45. Please enter radius of a circle
46. 19
47. Area of a circle is 1134.1149479459152
48. */

Calculate Circle Perimeter

1. /*
2. Calculate Circle Perimeter using Java Example
3. This Calculate Circle Perimeter using Java Example shows how to calculate
4. Perimeter of circle using it's radius.
5. */
7. import java.io.BufferedReader;
8. import java.io.IOException;
9. import java.io.InputStreamReader;
11. public class CalculateCirclePerimeterExample {
13. public static void main(String[] args) {
15. int radius = 0;
16. System.out.println("Please enter radius of a circle");
18. try
19. {
20. //get the radius from console
21. BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
22. radius = Integer.parseInt(br.readLine());
23. }
24. //if invalid value was entered
25. catch(NumberFormatException ne)
26. {
27. System.out.println("Invalid radius value" + ne);
28. System.exit(0);
29. }
30. catch(IOException ioe)
31. {
32. System.out.println("IO Error :" + ioe);
33. System.exit(0);
34. }
36. /*
37. * Perimeter of a circle is
38. * 2 * pi * r
39. * where r is a radius of a circle.
40. */
42. //NOTE : use Math.PI constant to get value of pi
43. double perimeter = 2 * Math.PI * radius;
45. System.out.println("Perimeter of a circle is " + perimeter);
46. }
47. }
49. /*
50. Output of Calculate Circle Perimeter using Java Example would be
51. Please enter radius of a circle
52. 19
53. Perimeter of a circle is 119.38052083641213
54. */