Get average of numbers : I am supposed to calculate the double of three numbers and get its average.
I am required to use the following two methods, no changing them:
getNumbers(); which only gets the user inputs. no returns, no arguments. 
getAverage(); which calculate the average of the three double numbers. returns the average, and has no argument.

My question is everytime I run it on CMD, it shows that method does not work and will not print an output. For me to enter three numbers, and get its average at the end. 
If someone can give me advice as to what I am doing wrong, it will be greatly appreciated. 


    import java.util.Scanner;
    public class ComputeAverage{
        double firstNum;
        double secondNum;
        double thirdNum; 
        double sum;
        double average;
        
        public void getNumbers(){
            Scanner keyboard = new Scanner(System.in);
            System.out.println("Enter your first number: ");
            double firstNum = keyboard.nextDouble();
            System.out.println("Enter your second number: ");
            double secondNum = keyboard.nextDouble();
            System.out.println("Enter your third number: ");
            double thirdNum = keyboard.nextDouble();
            Test.println("The average is: " + average);
        }
        public double getAverage(double firstNum, double secondNum, double thirdNum){
            double average = firstNum + secondNum + thirdNum / 3; 
            return average;  
          
        }
    }