示例代码：
//首字母转小写
public static String toLowerCaseFirstOne(String s){
if(Character.isLowerCase(s.charAt(0)))
return s;
else
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;
else
return (new StringBuilder()).append(Character.toUpperCase(s.charAt(0))).append(s.substring(1)).toString();
}