How can I write a function that returns the mathematical operator if two variables are equal to the third variable?

for example

public String mathFunction(4,2,6) returns "+",
public String mathFunction(2,2,4) returns "+*", (+ and *)
public String mathFunction(7,1,12) returns "None"

/* My Code */

public class mathFunction {
    public static void main(String... nums) {
        int num1, num2, num3;
        if (num1 * num2 == num3) { /*returns "*" if true */ 
            String multiply = public static String.valueOf(nums);
            System.out.println(multiply);
        }
        else if (num1 / num2 == num3) { /*returns "/" if true */ 
            String divide = public static String.valueOf(nums);
            System.out.println(divide);
        }
        else if (num1 + num2 == num3) {  /*returns "+" if true */                             
            String add = public static String.valueOf(nums);
            System.out.println(add);
        }
        else if (num1 - num2 == num3) { /*returns "-" if true */
            String subtract = public static String.valueOf(nums);
            System.out.println(subtract);
        }
        else {
            System.out.println("None")
        } 
    }
}