Java代码混乱

Question

好的，所以我试图找出whay，无论我输入什么性别，它告诉我性别无效。我的目标是让程序识别m或M或F或f作为性别，我认为我完成了.toUpperCase ...任何人都知道我缺少什么？

public class ChildHeight {

    public static void main(String[] args) 
    {
        Scanner keyboard = new Scanner(System.in); //iniate keyboard as scanner object


        String cGender;
        int hMotherFeet;
        int hMotherInches;
        int hFatherFeet;
        int hFatherInches;
        int hChild;
        int hMother;
        int hFather;

      //Prompts user for imput
        System.out.print("Please enter gender for a child (ex. m,F): ");
        cGender = keyboard.next();
        System.out.print("Please enter the number of feet in father's height: ");
        hFatherFeet = keyboard.nextInt();
        System.out.print("Please enter the number of inches in father's height: ");
        hFatherInches = keyboard.nextInt();
        System.out.print("Please enter the number of feet in mother's height: ");
        hMotherFeet = keyboard.nextInt();
        System.out.print("Please enter the number of inches in mother's height: ");
        hMotherInches = keyboard.nextInt();

      //adds inches to the converted inches from feet
        hMother = hMotherInches + ConvertToInches(hMotherFeet);
        hFather = hFatherInches + ConvertToInches(hFatherFeet);

      //takes parameters and based on gender points to formula to get childs height
        hChild = GetChildHeight(hMother, hFather, cGender);

      //Prints childs calculated height
        System.out.printf("The estimated child height is %d'%d\".", (hChild / 12), (hChild % 12));
    }

    //method to convert feet to inches
    public static int ConvertToInches(int feet)
    {
        return feet * 12;
    }

    public static int GetChildHeight(int mother, int father, String gender)
    {
        int child = 0;

        if (gender.toUpperCase() == "M")
        {
                child = ((mother * 13/12) + father)/2;
                }
            else if (gender.toUpperCase()== "F")
            {
                child = ((father * 13/12) + mother)/2;
            }
                else
            {
            System.out.println("Invalid gender. Gender must be M or F.");
                System.exit(0);

        }

        return  child;
    }
}