Converter .java

package main;

/**

* @author cm_wang

*

* 转换工具类

*/

public class Converter {

public static final String[][] str = {

{"","I","II","III","IV","V","VI","VII","VIII","IX"}, // 个位数举例

{"","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"}, // 十位数举例

{"","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"}, // 百位数举例

{"","M","MM","MMM"} // 千位数举例

};

/**

* @param nubmer

* @return

*

* 思路是：千位先除以1000然后模10，百位先除以100然后模10，十位先除以10然后模10，个位直接模10.

*/

public static String convert(String strNubmer) {

StringBuilder strBuilder = new StringBuilder();

int number = Integer.parseInt(strNubmer);

strBuilder.append(str[3][number/1000%10]);

strBuilder.append(str[2][number/100%10]);

strBuilder.append(str[1][number/10%10]);

strBuilder.append(str[0][number%10]);

return strBuilder.toString();

}

}

InputHelper.java

package main;

import java.util.regex.Pattern;

import java.util.regex.Matcher;

/**

* @author cm_wang

*

* 过滤工具类

*/

public class InputHelper {

/**

* @param str

* @return 过滤后的数字

*

* 过滤掉除了数字以外的所有非法字符。

*/

public static String getNumber(String str) {

String regEx = "[^0-9]";

Pattern p = Pattern.compile(regEx);

Matcher m = p.matcher(str);

return m.replaceAll("").trim();

}

}

Roman.java

package main;

import static main.Converter.*;

import static main.InputHelper.*;

import java.util.Scanner;

/**

* @author cm_wang

*

* main class.

*/

public class Roman {

@SuppressWarnings("resource")

public static void main(String[] args) throws Exception {

while(true){

System.out.println();

System.out.print("请输入0~3999的阿拉伯数字：");

Scanner sc = new Scanner(System.in);

String str = getNumber(sc.nextLine());

try {

System.out.println("转换后的罗马数字为：" + convert(str));

}catch(Exception e) {

System.out.println("非法字符，请输入数字！");

}

}

}

}