如何从没有构造函数的另一个类调用方法

Question

I'm having a bit of trouble on a program at school.

I have to call a method called factorial in my FactorialCalculator class through a method called factorial in my BCD class. Normally, I would do something like this:

FactorialCalculator newCalc = new FactorialCalculator(8);

However, factorial is the only method in the FactorialCalculator class, and I am not allowed to make any more methods, including a constructor.

Any suggestions?

Answer 1

Create it as a static method:

public class FactorialCalculator {
    public static int factorial(int number) {
        // Calculate factorial of number
    }
}

And you can call it this way:

int factorial = FactorialCalculator.factorial(5); // for the example

A static method is a method that is not associated with any instance of any class, & it can be accessed using the Classname.staticMethod( ) notation.

Answer 2

It's Simple, if you make it Static , You will be able to call it from another class. Create it as a static method:

class FactorialCalculator {
    public static int factorial(int number) {
        ...YourCode...
    }
}

And you can call it this way:

int number = 10;
int f = FactorialCalculator.factorial(number); 

Answer 3

如果它是一个静态方法，你会做FactorialCalculator.factorial(...) 。

Answer 4

You can either use a default constructor, which is just FactorialCalculator fc = new FactorialCalculator(); . Easy as that. However, it looks like your teacher wants you to create a static method. Static methods are sort of like utilities of a class, instead of being a function of an object. So, in your case, you should make FactorialCalculator be more of a utility class instead of an object class. public static int factorial(int num) {} should do the trick. This way, you can just go FactorialCalculator.factorial(5) as you did in your example.

Hope this helps!

Answer 5

First, you always have the standard constructor, which takes no parameters. So you can instatiate FactorialCalculator and then call its factoral -Method.