驼峰格式字符串转换为下划线格式字符串

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class GenUtils {
	
	public static final char UNDERLINE = '_';

	 /**
    * 驼峰格式字符串转换为下划线格式字符串
    * 
    * @param param
    * @return
    */
   public static String camelToUnderline(String param) {
       if (param == null || "".equals(param.trim())) {
           return "";
       }
        int len = param.length();
       StringBuilder sb = new StringBuilder(len);
       for (int i = 0; i < len; i++) {
           char c = param.charAt(i);
           if (Character.isUpperCase(c)) {
               sb.append(UNDERLINE);
               sb.append(Character.toLowerCase(c));
           } else {
               sb.append(c);
           }
       }
       return sb.toString();
   }
   
   
   public static void main(String[] ages) {
	   System.out.println(camelToUnderline("ABCddfANM"));
   }

}