⁴

小功能的Java标准代码也不容易

2026-09-03 03:53

阅读739

2026-09-03 03:53

阅读 739

/** 任务：从键盘上输入一个人的体重（公斤）和身高（米），计算BMI指数并输出体重状态体重指标（Body Mass Index）= 体重 / 身高的平方（kg/m2） BMI < 18.5 ：偏瘦 BMI < 24：正常 BMI < 27：偏胖 BMI < 30：肥胖 BMI >= 30：重度肥胖 */

自己写的代码

import java.util.Scanner;

class Bmi { private double weight; private double height; private double bmi; private String fat;

▼
text
复制代码
public Bmi(){}
public Bmi(double weight, double height){
    this.weight = weight;
    this.height = height;
}

public void getInfo(){
    System.out.println("您的体重是：" + this.weight + " kg，您的身高是：" + this.height + " cm");
}
public void setWeight(double weight){
    this.weight = weight;
}
public void setHeight(double height){
    this.height = height;
}
public double getWeight(){
    return this.weight;
}
public double getHeight(){
    return this.height;
}
public double getBmi(){
    bmi = weight / ((height / 100) * (height / 100));
    return this.bmi;
}
public String getFat(){
    if (bmi < 18.5) {this.fat = "偏瘦";}
    if (bmi < 24 && bmi > 18.5) {this.fat = "正常";}
    if (bmi < 27 && bmi > 24) { this.fat = "偏胖";}
    if (bmi < 30 && bmi > 27) {this.fat = "肥胖";}
    if (bmi >= 30) { this.fat = "重度肥胖";}
    return this.fat;
}

}

public class Java2026090108 {

▼
text
复制代码
public static void main(String[] args){
    
    Scanner sc = new Scanner(System.in);
    // 1、接收输入的体重
    System.out.print("请输入您的体重（公斤）：");
    double weight = sc.nextDouble();
    // 1、接收输入的身高
    System.out.print("请输入您的身高（厘米）：");
    double height = sc.nextDouble();
    Bmi bmi = new Bmi();
    bmi.setWeight(weight);
    bmi.setHeight(height);



    System.out.println();
    System.out.println("===========输入您的体重和身高，输出身体的健康BMI================\n");
    // 3、判断BMI
    bmi.getInfo();
    System.out.printf("%n您的BMI指标是：%,.2fkg/m2%n%n",bmi.getBmi());
    System.out.printf("您的体型属于：%s%n",bmi.getFat());

}

}

问题

1、空壳对象风险：提供了无参构造器 public Bmi(){}，可以创建出 weight=0, height=0 的非法对象 2、边界值黑洞：getFat() 用独立的 if 且条件互斥（如 bmi=18.5 时没有任何条件满足），返回 null 3、getter有副作用：getBmi() 在返回值的同时修改了成员变量 this.bmi 4、调用顺序依赖：getFat() 依赖 getBmi() 先被调用，否则 bmi 为 0.0 5、无参构造器绕过了校验：main 里用 new Bmi() + setter 赋值，完全没有参数合法性检查 6、Scanner未关闭：sc.close() 缺失 7、魔法数字：18.5、24、27、30 直接硬编码在方法里 8、注释与代码单位不一致：注释写"身高（米）"，实际按厘米处理（height / 100）

Kimi帮助下写的代码

`import java.util.Scanner;

class BMI { private static final double THIN = 18.5; // BMI阈值 private static final double NORMAL = 24; // BMI阈值 private static final double OVERWEIGHT = 27; // BMI阈值 private static final double OBESE = 30; // BMI阈值

▼
text
复制代码
private final double weight; // 体重，公斤
private final double height; // 身高，厘米

public BMI(double weight, double height) {
    if (weight <= 0 || height <= 0) {
        throw new IllegalArgumentException("体重和身高必须大于 0");
    }
    this.weight = weight;
    this.height = height;
}

@Override
public String toString() {
    return String.format("您的体重是：%.2f kg，身高：%.2f cm", weight, height);
}

public double getWeight() {
    return this.weight;
}

public double getHeight() {
    return this.height;
}

public double getBMI() {
    return weight / Math.pow((height / 100), 2);
}

public String getBMIStatus() {
    double bmi = getBMI();

    if (bmi < THIN) {
        return "偏瘦";
    } else if (bmi < NORMAL) {
        return "正常";
    } else if (bmi < OVERWEIGHT) {
        return "偏胖";
    } else if (bmi < OBESE) {
        return "肥胖";
    } else {
        return "重度肥胖";
    }
}

}

public class Java2026090109 {

▼
text
复制代码
public static void main(String[] args) {

    try (Scanner sc = new Scanner(System.in)) {
        // 判断输入是否合法？
        double weight = readPositiveDouble(sc, "请输入您的体重（公斤）：");
        double height = readPositiveDouble(sc, "请输入您的身高（厘米）：");

        BMI person = new BMI(weight, height);
        printResult(person);

    } catch (IllegalArgumentException e) {
        System.out.println("!系统错误：" + e.getMessage());
    }

}

private static void printResult(BMI person) {
    System.out.println("\n-------------------------------------------------------");
    System.out.println(person);
    System.out.println("=======================================================");
    System.out.printf("%n您的BMI指标是：%.2fkg/m\u00B2%n", person.getBMI());
    System.out.printf("您的体型属于：%s%n", person.getBMIStatus());
}

// 输入的时候就判断数据的合法性    
private static double readPositiveDouble(Scanner sc, String prompt) {
    while (true) {
        System.out.print(prompt);
        String line = sc.nextLine().trim(); // 去除两头的空格

        if (line.isEmpty()) {
            System.out.println(">>>错误！输入不能为空，请输入有效的数字！<<<\n");
            continue;
        }
        try {
            double value = Double.parseDouble(line);
            if (value <= 0) {
                System.out.println(">>>错误！输入值必须大于 0 ！！！请重新输入！<<<\n");
            } else {
                return value;
            }
        } catch (NumberFormatException e) {
            System.out.println(">>>错误：\"" + line + "\"不是有效的数字，请重新输入！<<<\n");
        }

    }
}

Kimi改的代码

import java.util.Scanner;

/**

BMI 体型分类枚举
每个枚举值持有：中文描述、BMI下限、BMI上限 */

enum BMIStatus { THIN("偏瘦", 0, 18.5), NORMAL("正常", 18.5, 24.0), OVERWEIGHT("偏胖", 24.0, 27.0), OBESE("肥胖", 27.0, 30.0), SEVERELY_OBESE("重度肥胖", 30.0, Double.MAX_VALUE);

▼
text
复制代码
private final String description;  // 中文描述
private final double min;          // 区间下限（包含）
private final double max;          // 区间上限（不包含）

// 枚举构造器默认就是 private，可以省略 private 关键字
BMIStatus(String description, double min, double max) {
    this.description = description;
    this.min = min;
    this.max = max;
}

public String getDescription() {
    return description;
}

/**
 * 根据 BMI 值查找对应的分类
 */
public static BMIStatus fromBMI(double bmi) {
    for (BMIStatus status : values()) {
        if (bmi >= status.min && bmi < status.max) {
            return status;
        }
    }
    throw new IllegalArgumentException("无法识别的 BMI 值: " + bmi);
}

@Override
public String toString() {
    return description;
}

}

class BMI { private final double weight; private final double height;

▼
text
复制代码
public BMI(double weight, double height) {
    if (weight <= 0 || height <= 0) {
        throw new IllegalArgumentException("体重和身高必须大于 0");
    }
    this.weight = weight;
    this.height = height;
}

@Override
public String toString() {
    return String.format("体重：%.1f kg，身高：%.1f cm", weight, height);
}

public double getWeight() {
    return weight;
}

public double getHeight() {
    return height;
}

public double getBMI() {
    return weight / Math.pow(height / 100.0, 2);
}

/**
 * 返回值从 String 升级为 BMIStatus 枚举
 */
public BMIStatus getBMIStatus() {
    return BMIStatus.fromBMI(getBMI());
}

}

public class Java2026090109 {

▼
text
复制代码
public static void main(String[] args) {
    try (Scanner sc = new Scanner(System.in)) {
        double weight = readPositiveDouble(sc, "请输入您的体重（公斤）：");
        double height = readPositiveDouble(sc, "请输入您的身高（厘米）：");

        BMI person = new BMI(weight, height);
        printResult(person);
    } catch (IllegalArgumentException e) {
        System.out.println("系统错误：" + e.getMessage());
    }
}

private static void printResult(BMI person) {
    System.out.println("\n-------------------------------------------------------");
    System.out.println(person);
    System.out.println("=======================================================");
    System.out.printf("%n您的 BMI 指标是：%.2f kg/m\u00B2%n%n", person.getBMI());
    
    // %s 会自动调用枚举的 toString()，输出中文描述
    System.out.printf("您的体型属于：%s%n", person.getBMIStatus());
}

private static double readPositiveDouble(Scanner sc, String prompt) {
    while (true) {
        System.out.print(prompt);
        String line = sc.nextLine().trim();

        if (line.isEmpty()) {
            System.out.println(">>> 错误！输入不能为空，请输入有效的数字！");
            continue;
        }

        try {
            double value = Double.parseDouble(line);
            if (value <= 0) {
                System.out.println(">>> 错误！输入值必须大于 0，请重新输入！");
            } else {
                return value;
            }
        } catch (NumberFormatException e) {
            System.out.println(">>> 错误：\"" + line + "\" 不是有效的数字，请重新输入！");
        }
    }
}

}