Common methods for data conversion in java POI parsing Excel

public static String reThreeStr(String ss){
 
      boolean result= ss.matches("^[-+]?(([0-9]+)([.]([0-9]+))?|([.]([0-9]+))?)$"); 
      if(result&&ss!=null&&!"".equals(ss)){
        Double sss=Double.valueOf(ss);
      String numStr=new java.text.DecimalFormat("0.000").format(sss);
      Double lsDou=Double.valueOf(numStr);
      ss=String.valueOf(lsDou);
      }
    return ss;
  }
 
public static BigDecimal reThreeBig(BigDecimal ss){
  String numStr=new java.text.DecimalFormat("0.000").format(ss);
  BigDecimal newNum=new BigDecimal(numStr);
  return newNum;
}
  public static String delezero(String old){
     boolean result= old.matches("^[-+]?(([0-9]+)([.]([0-9]+))?|([.]([0-9]+))?)$");
     if(result&&old!=null&&!"".equals(old)){
       String newStr=old;
        if(old.contains(".0")){
          old=newStr.substring(0, old.length()-2);
        }
        return old;
     }else{
       return old;
     }
     
  }