using static method

Question

I'm unsure how to use the static method in this program. I am coding a program that will calculate a factorial of a number between 0 and 10. The user can enter the number and the program should calculate the factorial. I had originally written a functional program with all of the code coming from the main and then when I double checked the assignment rubric I noticed I was supposed to place the calculation for getting the factorial in a static method. I believe my issue is towards the bottom where I'm asking the user to enter the number I don't send it to the calculator. I guess I'm unclear on how that is done. I'm new so I apologize for my poor coding and I appreciate any help.

Here is my code:

import java.util.Scanner; //import scanner class
public class FactorialCalculator {
 public static long calculator(long fact, int num) {
 for(int i = 1; i<=num; i++) {
 fact *= i;
 }
 return fact;
 }
 public static void main(String[] args) {
 Scanner calc = new Scanner(System.in); //create new scanner calc
 int num = 0;
 long fact = 1;
 //welcome user to the Factorial Calculator
 System.out.println("Welcome to the Factorial Calculator.");
 System.out.println();
 String choice = "y";
 while (choice.equalsIgnoreCase("y")) {
 System.out.println("Please enter an integer that's greater than 0 and less than 10: ");
 num = calc.nextInt();
 System.out.println("The Factorial for " + num + " is " + fact +".");
 System.out.println();
 System.out.println("Would you like to continue? y/n");
 choice = calc.next();
 System.out.println();
 }
 }
}

• Michael Burr: As a side note - the method that calculates the factorial should only need one input parameter - get rid of the first parameter and initialize it in the method.
• Hawken: @MichaelBurr That should be done, as right now fact is not reset between loops. Keep in mind that fact has to be declared in the calculator method long fact=1; as well as in main().
• Luiggi Mendoza: a static method can invoke only another static methods from the same class. Your main method is static, so if you want to call calculator it must be static too. You can refer to the static keyword here or to this post.
• Jeremy B: @LuiggiMendoza Thank you for the links. I have to revisit them but what I read was a little more helpful than what I was reading from.
• Luiggi Mendoza: @JeremyBorton sure just google java static keyword and there will be tons of info for you. Maybe you want to learn more of Java keywords and their use :D.

Answer 1

Place this just before you print the result:

fact = FactorialCalculator.calculator(fact, num)

Answer 2

You're never calling calculator(long fact, int num);

just call it with

 fact = calculator(fact,num);

right after:

 num = calc.nextInt();

EDIT:

I would recommend you also remove the long fact as an argument to calculator() and add it into the method body of calculator()

Ex:

public static long calculator(int num){
 long fact=1;
 for(int i = 1; i<=num; i++){
 fact *= i;
 }
 return fact;
}

• Jeremy B: I'm noticing now my calculations are off when they weren't before. in my main method I did delcare int num = 0; and long fact = 1; if I don't have that then I get errors is there a way around this?

Answer 3

You can call a static method of a class as:

variableType variableName = ClassName.MethodName(parameters);

In your case you can simply call:

 fact = FactorialCalculator.calculator(fact, num);

It should be inserted somewhere AFTER when you ASK the user for the input num, and BEFORE you print out the fact number to the user

Answer 4

import java.util.Scanner; //import scanner class
public class FactorialCalculator 
{
 public static long calculator(int num)
 {
 long fact = 1;
 for(int i = 1; i<=num; i++)
 {
 fact *= i;
 }
 return fact;
 }
 public static void main(String[] args)
 {
 Scanner calc = new Scanner(System.in); //create new scanner calc
 int num;
 //welcome user to the Factorial Calculator
 System.out.println("Welcome to the Factorial Calculator.");
 System.out.println();
 String choice = "y";
 while (choice.equalsIgnoreCase("y"))
 {
 System.out.println("Please enter an integer that's greater than 0 and less than 10: ");
 num = calc.nextInt();
 fact = FactorialCalculator.calculator(num);
 System.out.println("The Factorial for " + num + " is " + fact +".");
 System.out.println();
 System.out.println("Would you like to continue? y/n");
 choice = calc.next();
 System.out.println();
 }
 }
}

• Hawken: You may want to offer an explanation for what you are changing.

Answer 5

Start with this:

fact = FactorialCalculator.calculator(fact, num)

And you should notice that the program will calculate factorial right for the first time, then it starts to fail since the second time. Fixing that bug is your job.

Answer 6

As your calculator method is a static method so you can call it directly by using the class name.

num = calc.nextInt();
long result_factorial = FactorialCalculator.calcuator(fact,num)

Your method should be

public static long (int num)
 {
 long fact = 1;
 for(int i = 1; i<=num; i++)
 {
 fact *= i;
 }
 return fact;
 }

Remove the fact initialisation from your main method.

• MByD: You shouldn't create an object, it's a static method.
• RanRag: @BinyaminSharet: I was trying to explain the difference between static and instance method but than i dropped that idea but forgot to remove my sentence.
• Hawken: @RanRag it's in the same class, you can simply call it as calculator(); not FactorialCalculator.calcuator();
• RanRag: @Hawken: I know that but was trying to do it the general way.What if not in same class.?
• RanRag: @Hawken: That is how i called it. FactorialCalculator.calcuator(fact,num)