Java罗马数字转换器：基础实现与常见陷阱解析

package jfauvelle_G10_A04;

public class RomanNumeral {
    private String romanNum = "";
    private int decimalNum = 0;

    // 无参构造函数
    public RomanNumeral() {
        romanNum = "";
        decimalNum = 0;
    }

    // 接收罗马数字字符串的构造函数
    public RomanNumeral(String r) {
        // 在构造时进行转换，确保decimalNum也得到初始化
        this.romanNum = r;
        this.decimalNum = convertRomanToInteger(r);
    }

    // 接收整数的构造函数
    public RomanNumeral(int i) {
        // 在构造时进行转换，确保romanNum也得到初始化
        this.decimalNum = i;
        this.romanNum = convertIntegerToRoman(i);
    }

    // Getter和Setter方法
    public void setRomanNumeral(String r) {
        this.romanNum = r;
        // 关键：当设置罗马数字时，同时更新其对应的十进制值，保持对象状态一致
        this.decimalNum = convertRomanToInteger(r);
    }

    public String getRomanNumeral() {
        return romanNum;
    }

    public void setDecimalNumeral(int i) {
        this.decimalNum = i;
        // 关键：当设置十进制值时，同时更新其对应的罗马数字，保持对象状态一致
        this.romanNum = convertIntegerToRoman(i);
    }

    public int getDecimalNumeral() {
        return decimalNum;
    }

    // ... 转换方法将在后续章节详细介绍
}

    public String convertIntegerToRoman(int r) {
        int roman = r;
        String finalRoman = "";

        // 从大到小依次处理罗马数字值
        while (roman >= 1000) {
            finalRoman = finalRoman + "M";
            roman -= 1000;
        }

        while (roman >= 500) {
            finalRoman = finalRoman + "D";
            roman -= 500;
        }

        while (roman >= 100) {
            finalRoman = finalRoman + "C";
            roman -= 100;
        }

        while (roman >= 50) {
            finalRoman = finalRoman + "L";
            roman -= 50;
        }

        while (roman >= 10) {
            finalRoman = finalRoman + "X";
            roman -= 10;
        }

        while (roman >= 5) {
            finalRoman = finalRoman + "V";
            roman -= 5;
        }

        while (roman >= 1) {
            finalRoman = finalRoman + "I";
            roman -= 1;
        }

        return finalRoman;
    }

    private int convertRomanToInteger(String n) {
        String romanStr = n; // 使用更具描述性的变量名
        int finalDecimal = 0;

        // 修正：循环条件应为 i < romanStr.length()
        for (int i = 0; i < romanStr.length(); i++) {
            char currentChar = romanStr.charAt(i); // 获取当前字符

            // 修正：将while循环改为if条件判断
            if (currentChar == 'M') {
                finalDecimal += 1000;
            } else if (currentChar == 'D') { // 使用else if 提高效率，避免不必要的判断
                finalDecimal += 500;
            } else if (currentChar == 'C') {
                finalDecimal += 100;
            } else if (currentChar == 'L') {
                finalDecimal += 50;
            } else if (currentChar == 'X') {
                finalDecimal += 10;
            } else if (currentChar == 'V') {
                finalDecimal += 5;
            } else if (currentChar == 'I') {
                finalDecimal += 1;
            }
            // 如果遇到不识别的字符，这里可以添加错误处理逻辑
        }
        return finalDecimal;
    }

public class RomanNumeralCalculatorTestCase {

    public static void main(String[] args) {
        boolean working = true;

        // 测试空构造函数和setter
        RomanNumeral case1 = new RomanNumeral();
        case1.setRomanNumeral("XVI"); // 设置罗马数字，内部会转换为十进制
        // 修正：字符串比较使用 .equals()
        if (!case1.getRomanNumeral().equals("XVI")) {
            working = false;
            System.err.println("ERROR: Roman numeral was not set properly. It is " + case1.getRomanNumeral()
                    + ". It should be XVI");
        }
        // 验证十进制值是否同步更新
        if (case1.getDecimalNumeral() != 16) { // XVI = 16
            working = false;
            System.err.println("ERROR: Decimal number was not updated properly after setting Roman. It is " + case1.getDecimalNumeral()
                    + ". It should be 16");
        }

        case1.setDecimalNumeral(2004); // 设置十进制，内部会转换为罗马数字
        if (case1.getDecimalNumeral() != 2004) {
            working = false;
            System.err.println("ERROR: Decimal number was not set properly. It is " + case1.getDecimalNumeral()
                    + ". It should be 2004");
        }
        // 验证罗马数字是否同步更新 (2004 = MMIIII)
        if (!case1.getRomanNumeral().equals("MMIIII")) { // 根据本教程规则 2004 = MMIIII
            working = false;
            System.err.println("ERROR: Roman numeral was not updated properly after setting Decimal. It is " + case1.getRomanNumeral()
                    + ". It should be MMIIII");
        }


        // 测试整数构造函数
        RomanNumeral case2 = new RomanNumeral(1000);
        String s = "M";
        if (!(case2.getRomanNumeral().equals(s))) { // 修正：字符串比较使用 .equals()
            working = false;
            System.err.println("ERROR: Roman numeral from int constructor is incorrect. It is " + case2.getRomanNumeral()
                    + ", it should be M.");
        }
        if (case2.getDecimalNumeral() != 1000) {
            working = false;
            System.err.println("ERROR: Decimal number from int constructor is incorrect. It is " + case2.getDecimalNumeral()
                    + ". It should be 1000");
        }

        // 测试字符串构造函数
        RomanNumeral case3 = new RomanNumeral("M");
        if (case3.getDecimalNumeral() != 1000) {
            working = false;
            System.err.println("ERROR: Decimal number from string constructor is incorrect. It is " + case3.getDecimalNumeral()
                    + ". It should be 1000");
        }
        if (!case3.getRomanNumeral().equals("M")) { // 修正：字符串比较使用 .equals()
            working = false;
            System.err.println("ERROR: Roman numeral from string constructor is incorrect. It is " + case3.getRomanNumeral()
                    + ". It should be M");
        }

        if (working)
            System.out.print("Congratz ! The test case work !");
    }
}