工作中遇到的奇葩需求

package com.hsi.utils;import java.util.Arrays;import java.util.List;public class AddString {	private static String qq ="";	private static int num=0;	/**	 * 实现字符串+1	 * 如ab9Z变为ac0A，	 * @param a	 * @return	 */	public static String returnString (String a) {		//判断是否为纯数字		qq = a;		try{			Integer pcode = Integer.valueOf(qq).intValue()+1;			qq = ""+pcode;					}catch(Exception e){						qq = bre(String.valueOf(qq.charAt(qq.length()-1)));		}		return qq;	}		public static String bre(String az) {		String y[] = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"};		 List list = Arrays.asList(y);			for (int k = 0; k < y.length; k++) {				if(qq.length()-num<0){					break;				}				if(az.equals("Z")){					//当等Z的时候，这个时候取的应该是A										StringBuffer sb = new StringBuffer(qq);					sb.replace(qq.length()-num-1, qq.length()-num, "A");					qq = sb.toString();					num++;					qq = bre(String.valueOf(qq.charAt(qq.length()-1-num)));					return qq;									}				 else if (az.equals("z")) {					 StringBuffer sb = new StringBuffer(qq);					sb.replace(qq.length()-num-1, qq.length()-num, "a");					qq = sb.toString();					 //qq = qq.substring(0,qq.length()-1)+"0";					num++;					 qq = bre(String.valueOf(sb.toString().charAt(sb.toString().length()-1-num)));					 return qq;				}				 else if (az.equals("9")) {					 StringBuffer sb = new StringBuffer(qq);						sb.replace(qq.length()-num-1, qq.length()-num, "0");						qq = sb.toString();						num++;					 qq = bre(String.valueOf(sb.toString().charAt(sb.toString().length()-1-num)));					 return qq;				}				else{					if(num > 0){					if(!isNum(String.valueOf(qq.charAt(qq.length()-1-num)))){						StringBuffer sb = new StringBuffer(qq);						sb.replace(qq.length()-1-num, qq.length()-num, y[list.indexOf(az)+1]);						qq = sb.toString();					}					if(isNum(String.valueOf(qq.charAt(qq.length()-1-num)))){						StringBuffer sb = new StringBuffer(qq);						int ss = Integer.valueOf(String.valueOf(qq.charAt(qq.length()-1-num))).intValue()+1;						sb.replace(qq.length()-1-num, qq.length()-num, ""+ss);						qq = sb.toString();					}}					else{						StringBuffer sb = new StringBuffer(qq);						sb.replace(qq.length()-num-1, qq.length()-num, y[list.indexOf(az)+1]);						qq = sb.toString();					}					return qq;				}			}			return null;	}	public static boolean isNum(String str){ 		return str.matches("^[-+]?(([0-9]+)([.]([0-9]+))?|([.]([0-9]+))?)$"); 	} }