Java获取首字符串大小写

    public static String firstCharToLowerCase(String str) {        char firstChar = str.charAt(0);        if (firstChar >= 'A' && firstChar <= 'Z') {            char[] arr = str.toCharArray();            arr[0] += ('a' - 'A');            return new String(arr);        }        return str;    }    public static String firstCharToUpperCase(String str) {        char firstChar = str.charAt(0);        if (firstChar >= 'a' && firstChar <= 'z') {            char[] arr = str.toCharArray();            arr[0] -= ('a' - 'A');            return new String(arr);        }        return str;    }