java - 输出有问题

Question

这就是我必须做的“编写一个 java 应用程序，提示输入该人的信息，实例化该人的 Health Profile 类的对象，并打印该对象中的信息 - 包括该人的名字，姓氏、性别、出生日期、高度和体重——然后计算并打印该人的年龄、BMI、最大心率和目标心率范围。它还应该显示练习 2 中的“BMI 值”图表。 33 。”但是每当我运行它时我都会收到错误。

这是代码:

import java.util.*;
public class HealthProfile {

String firstName;
String lastName;
char gender;
int BirthMonth;
int BirthDay;
int BirthYear;
int height;
int weight;

public HealthProfile(String fName, String lName, char Genderr, int birthMonth, int birthDay, int birthYear, int heightt, int weightt){
    firstName = fName;
    lastName = lName;
    gender = Genderr;
    BirthMonth = birthMonth;
    BirthDay = birthDay;
    BirthYear = birthYear;
    height = heightt;
    weight = weightt;



}

    HealthProfile() {

    }

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

    public String getFirstName() {
        return firstName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setGender(char gender) {
        this.gender = gender;
    }

    public char getGender() {
        return gender;
    }

    public void setBirthMonth(int BirthMonth) {
        this.BirthMonth = BirthMonth;
    }

    public int getBirthMonth() {
        return BirthMonth;
    }

    public void setBirthDay(int BirthDay) {
        this.BirthDay = BirthDay;
    }

    public int getBirthDay() {
        return BirthDay;
    }

    public void setBirthYear(int BirthYear) {
        this.BirthYear = BirthYear;
    }

    public int getBirthYear() {
        return BirthYear;
    }

    public void setHeight(int height) {
        this.height = height;
    }

    public double getHeight() {
        return height;
    }

    public void setWeight(int weight) {
        this.weight = weight;
    }

    public double getWeight() {
        return weight;
    }

public int Age(){
Calendar now = Calendar.getInstance();
int nowYear = now.get(Calendar.YEAR);
int nowMonth = now.get(Calendar.MONTH);
int nowDay = now.get(Calendar.DATE);
int day = now.get(Calendar.DATE);
int month = now.get(Calendar.MONTH);
int year = now.get(Calendar.YEAR);
if (nowMonth > BirthMonth);
return (nowYear - BirthYear);
    }

public double getBMI(){
    return (weight * 703)/(height * height);
}

public int MaxHeartRate(){
 return 220-Age();
}

public double TargetHeartRate(){
return MaxHeartRate() * 0.85 + MaxHeartRate() * 0.5;
 }
}

这是测试部分:

import java.util.Scanner;

public class HealthProfileTest {
public static void main(String[] args) {
       Scanner input = new Scanner(System.in);
        String firstName;
        String lastName;
        String DoB;
        String theMonth;
        String theDay;
        String theYear;
        char gender;
        int Month;
        int Day;
        int Year;
        double height = 0.0;
        double weight;
       HealthProfile personalInfo = new HealthProfile();
       System.out.println("Enter your first name: ");
       firstName = input.nextLine();
       System.out.println("Enter your last name: ");
       lastName = input.nextLine();
       System.out.println("Male or female: ");
       gender = input.nextLine().charAt(0);
       System.out.println("Enter your date of birth in mm/dd/yyyy format: ");
       DoB = input.nextLine();
       theMonth = DoB.substring(0,2);
       theDay = DoB.substring(3,5);
       theYear = DoB.substring(6,10);
       Month = Integer.parseInt(theMonth);
       Day = Integer.parseInt(theDay);
       Year = Integer.parseInt(theYear);
       System.out.println("Enter your height in inches: ");
       height = input.nextInt();
       System.out.println("Enter your weight in pounds: ");
       weight = input.nextInt();
       System.out.println("Name: " + personalInfo.getFirstName() + personalInfo.getLastName());
       System.out.println("Gender: " + personalInfo.getGender());
       System.out.println("DoB: " + personalInfo.getBirthMonth() + "/" + personalInfo.getBirthDay() + "/" + personalInfo.getBirthYear());
       System.out.println("Height: " + personalInfo.getHeight());
       System.out.println("Weight: " + personalInfo.getWeight());
       System.out.println("Age: " + personalInfo.Age());
       System.out.println("BMI: " + personalInfo.getBMI());
       System.out.printf("Max heart rate: ", personalInfo.MaxHeartRate());
       System.out.printf("Target heart rate: ", personalInfo.TargetHeartRate());
       System.out.println(" ");
       System.out.println( "BMI VALUES" );
        System.out.println("Underweight: Under 18.5");
        System.out.println("Normal: 18.5-24.9 ");
        System.out.println("Overweight: 25-29.9");
        System.out.println("Obese: 30 or over");
    }
    }

这是输出:

Name: nullnull
Gender: 
DoB: 0/0/0
Height: 0.0
Weight: 0.0
Age: 2013
Exception in thread "main" java.lang.ArithmeticException: / by zero
        at HealthProfile.getBMI(HealthProfile.java:108)
        at HealthProfileTest.main(HealthProfileTest.java:43)
Java Result: 1

我知道我做的一切都是对的，但就是不明白为什么会出现这种情况。

Answer 1

您忘记调用方法setHeight和setWeight。因此，由于这些值是数字基元类型，因此默认情况下它们仍然为 0。显然，2 个零值的乘积等于 0，然后除以 0 会产生 ArithmeticException

尝试在接受输入后调用方法。

System.out.println("Enter your height in inches: ");
height = input.nextInt();
personalInfo.setHeight((int) height);
System.out.println("Enter your weight in pounds: ");
weight = input.nextInt();
personalInfo.setWeight((int) weight);

类似地设置“出生”字段

personalInfo.setBirthMonth(Month);
personalInfo.setBirthDay(Day);
personalInfo.setBirthYear(Year);

旁白:Java 命名约定表明变量以小写字母开头，例如日、月和年 >。了解它们 here