Modify the MyMath class: Add a method to calculate the factorial of a number. A

Question

Modify the MyMath class:

Add a method to calculate the factorial of a number. A factorial is calculation that multiplies together all of the numbers between 1 and the specified number. For instance, 5! (the ! symbol is used to denote factorial) is 1 * 2 * 3 * 4 * 5 = 120. 4! = 1 * 2 * 3 * 4 = 24.

Use a for loop to calcuate the factorial.

Make the method static.

Do not ask for any input in the MyMath class. Do not create a Scanner object. The factorial method should take one parameter and return a value.

Modify the Test class:

Do not create a MyMath object.

Gather all user input in the Test class. Do not ask for any input in the MyMath class.

Modify the menu for the user:

Add an option to find the factorial of a number.

Add an option to quit.

Use a while or do-while loop to repeat the program until the user chooses to quit.

*** This is what I have so far

14 import java.text.DecimalFormat;
15
16 public class MyMath {
17
18 /**
19 * method to return area of circle
20 *
21 * @param radius
22 * @return
23 */
24 public static double getCircleArea(double radius) {
25 DecimalFormat decimalFormat = new DecimalFormat("#.000");
26 double area = Double
27 .parseDouble(decimalFormat.format(radius * Math.PI));
28 return area;
29 }
30
31 /**
32 * method to return max number
33 *
34 * @param num1
35 * @param num2
36 * @return
37 */
38 public static int getMax(int num1, int num2) {
39 if (num1 < num2)
40 return num2;
41 else
42 return num1;
43 }
44
45 }

8 import java.util.Scanner;
9
10 public class MyMathTest {
11
12 /**
13 * @param args
14 */
15 public static void main(String[] args) {
16
17 Scanner scanner = null;
18 try {
19 scanner = new Scanner(System.in);
20
21 do {
22 int choice;
23 System.out.println("***Menu***");
24 System.out.println("1. Area");
25 System.out.println("2. Max");
26 System.out.println("0. Exit");
27 System.out.print("Enter your choce:");
28 choice = scanner.nextInt();
29 if (choice == 0)
30 break;
31 switch (choice) {
32 case 1: {
33 System.out.print("Enter the radius :");
34 double radius = scanner.nextDouble();
35 System.out.println("Area of Circle:"
36 + MyMath.getCircleArea(radius));
37 }
38 break;
39 case 2: {
40 System.out.print("Enter the First number:");
41 int num1 = scanner.nextInt();
42 System.out.print("Enter the Second number:");
43 int num2 = scanner.nextInt();
44 System.out.println("Max of Two numbers:"
45 + MyMath.getMax(num1, num2));
46 }
47 break;
48
49 default:
50 System.out.println("Invalid Choice Selected!");
51 break;
52 }
53 } while (true);
54
55 } catch (Exception e) {
56 // TODO: handle exception
57 }
58 }
59 }

Explanation / Answer

MyMathTest.java

import java.util.Scanner;

public class MyMathTest {

public static void main(String[] args) {

Scanner scanner = null;
try {
scanner = new Scanner(System.in);

do {
int choice;
System.out.println("***Menu***");
System.out.println("1. Area");
System.out.println("2. Max");
System.out.println("3. Factorial");
System.out.println("0. Exit");
System.out.print("Enter your choce:");
choice = scanner.nextInt();
if (choice == 0)
break;
switch (choice) {
case 1: {
System.out.print("Enter the radius :");
double radius = scanner.nextDouble();
System.out.println("Area of Circle:"
+ MyMath.getCircleArea(radius));
}
break;
case 2: {
System.out.print("Enter the First number:");
int num1 = scanner.nextInt();
System.out.print("Enter the Second number:");
int num2 = scanner.nextInt();
System.out.println("Max of Two numbers:"
+ MyMath.getMax(num1, num2));
}
break;
case 3:
   System.out.print("Enter the factorial number:");
   int num1 = scanner.nextInt();
   System.out.println("Fqactorial of "+num1+"! is :"
           + MyMath.factorial(num1));
   break;
default:
System.out.println("Invalid Choice Selected!");
break;
}
} while (true);

} catch (Exception e) {
// TODO: handle exception
}
}
}

MyMath.java

import java.text.DecimalFormat;

public class MyMath {

public static double getCircleArea(double radius) {
DecimalFormat decimalFormat = new DecimalFormat("#.000");
double area = Double
.parseDouble(decimalFormat.format(radius * Math.PI));
return area;
}
public static int factorial(int n){
   int fact = 1;
   for(int i=1; i<=n; i++){
       fact = fact * i;
   }
   return fact;
}

/**
* method to return max number
*
* @param num1
* @param num2
* @return
*/
public static int getMax(int num1, int num2) {
if (num1 < num2)
return num2;
else
return num1;
}

}

Output:

***Menu***
1. Area
2. Max
3. Factorial
0. Exit
Enter your choce:1
Enter the radius :2
Area of Circle:6.283
***Menu***
1. Area
2. Max
3. Factorial
0. Exit
Enter your choce:2
Enter the First number:4
Enter the Second number:3
Max of Two numbers:4
***Menu***
1. Area
2. Max
3. Factorial
0. Exit
Enter your choce:3
Enter the factorial number:5
Fqactorial of 5! is :120
Invalid Choice Selected!
***Menu***
1. Area
2. Max
3. Factorial
0. Exit
Enter your choce:0

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