public static String toLowerCaseFirstOne(String s){
  if(Character.isLowerCase(s.charAt(0)))
    return s;
    return (new StringBuilder()).append(Character.toLowerCase(s.charAt(0))).append(s.substring(1)).toString();

//首字母转大写
public static String toUpperCaseFirstOne(String s){
  if(Character.isUpperCase(s.charAt(0)))
    return s;
    return (new StringBuilder()).append(Character.toUpperCase(s.charAt(0))).append(s.substring(1)).toString();