BMI计算器Java

Question

我正在创建一个BMI计算器，但是我在运行程序时遇到了问题，因为我的结果是：

值为0.0，身高为0.0。你的体重指数是

当它应该说明名字，体重，体重指数，以及它是体重不足，健康，超重，还是肥胖。

以下是代码：

public class Person {

    private String firstName;
    private double  heightInches;
    private double weightPounds;


    public Person (String userFirstName, double userHeightInches, double userWeightPounds)
    {


        this.firstName = firstName;
        this.heightInches = heightInches;
        this.weightPounds = weightPounds;


    }



    public String getFirstName()
    {
        return this.firstName;
    }

    public double getHeightInches()
    {
        return this.heightInches;
    }

    public double getWeightPounds()
    {
        return this.weightPounds;
    }

    public void setFirstName (String firstName)
    {
        this.firstName = firstName;
    }

    public void setHeightInches(double userHeightInches)
    {
        this.heightInches = userHeightInches;
    }

    public void setWeightPounds(double userWeightPounds)
    {
        this.weightPounds = userWeightPounds;
    }





    @Override
    public String toString()
    {
        return this.firstName + "weighs " + this.weightPounds + " and measures  "
               + this.heightInches + " tall. Your BMI is "; 
    }



     public double calculateBMI(double userHeightInches,  double userWeightPounds )

    {


    double BMI = ((userWeightPounds / userHeightInches) * (userHeightInches)) * 703;
    return BMI;


    }

还有..。

public class BodyMassIndex {
    public static Person anyPerson;
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) 

    {

          createPersonObject();
          displayBMI();

    }

    public static void createPersonObject()
    {

        Scanner keyboard = new Scanner(System.in);


        System.out.println("What is your first name?");
        String firstName = keyboard.next();


        System.out.println ("How tall are you (in inches)?");
        Double heightInches = keyboard.nextDouble();



        System.out.println("How much do you weigh (in pounds)?");
        Double weightPounds = keyboard.nextDouble();

        anyPerson = new Person(firstName, heightInches, weightPounds);
    }

    public static void displayBMI()
    {


        double userWeightPounds = 0;
        double userHeightInches = 0;


        double BMI = anyPerson.calculateBMI(userWeightPounds, userHeightInches);

        System.out.println(anyPerson.toString());

        if (BMI < 18.5)
        {
            System.out.println("Underweight");
        }

        else if (BMI >= 18.5 && BMI < 24.9) {
            System.out.println("Healthy");
        }

        else if (BMI >= 25 && BMI < 29.9) {
            System.out.println("Overweight");
        }

        else if (BMI >= 30) {
            System.out.println("Obese");
        }

    }

Answer 1

您正在将字段变量设置为自身，这些变量没有实例化，因此值为null或0.0。您需要将它们设置为类的参数: this.firstName =this.firstName

您的BMI计算也是关闭的，因为您自动使用的值为0.0和0.0。您应该使用Person类中的getter方法来进行计算。

Answer 2

你应该按以下方式计算BMI吗？

public static void displayBMI() {

  /* This code is no longer needed */
  double userWeightPounds = 0;
  double userHeightInches = 0;

  double BMI = anyPerson.calculateBMI(anyPerson.getWeightPounds(), anyPerson.getHeightInches());
  ...

您还可以进一步简化代码，使Person不必要求将体重和身高作为参数来计算BMI：

public double calculateBMI() {
   return ((this.weightPounds / this.heightInches) * (this.heightInches)) * 703;

}

最好也检查一下零输入。