Java“脂肪克计算器”编程我试图需要验证输入，我得到了一个点，我需要验证用户的输入，考虑到以前的输入从另一个模块，与给定的公式.我正在尝试这一点，我不知道如何做到这一点，而不要求用户输入同样的事情了，请帮助问题是在这一行：

while(input < 0.0 || input < (fatGrams * 9)){

在下面的代码中

import java.util.Scanner;
class fatCalculator {

    public static void main(String[] args) {
        // Local variables
        double fatGrams, calories;

        // Calls getFat
        fatGrams = getFat();
        // Calls getCalories
        calories = getCalories();
        // Calls showPercent
        showPercent(fatGrams, calories);
    }
    public static double getFat() {
        Scanner keyboard = new Scanner(System.in);

        // Local variable
        double input;

        // Get the fat grams  
        System.out.println("Please enter the number of fat grams: ");
        input = keyboard.nextDouble();

        // Valitdate
        while (input < 0.0) {
            System.out.println("The number of fat grams cannot be less than 0.");
            System.out.println("Please enter the number of fat grams.");
            input = keyboard.nextDouble();
        }
        return input;
    }
    public static double getCalories() {
        Scanner keyboard = new Scanner(System.in);

        // Local variable
        double input;
        // call fatGrams

        // Get the calories
        System.out.println("Please enter the number of calories: ");
        input = keyboard.nextDouble();

        // Validate
        while (input < 0.0 || input < (fatGrams * 9)) { // <<<<<< PROBLEM IS HERE
            System.out.println("The number of calories cannot be less than the number of fat grams * 9.");
            System.out.println("Please enter the number of calories.");
            input = keyboard.nextDouble();
        }
        return input;
    }
    public static void showPercent(double fatGrams, double calories) {
        // local varibale
        double finalPercentage;

        // Calculate and display final percentage
        finalPercentage = (fatGrams * 9) / calories;
        System.out.println("The percentage of calories from fat is " + finalPercentage);
        // Banner
        while (finalPercentage < 0.3) {
            System.out.println("That food item is considered" + "low fat.");
        }
    }
}