### Question:
StringUtils extends org.apache.commons.lang3.StringUtils { public static String toCamelCase(String s) { if (s == null) { return null; } s = s.toLowerCase(); StringBuilder sb = new StringBuilder(s.length()); boolean upperCase = false; for (int i = 0; i < s.length(); i++) { char c = s.charAt(i); if (c == SEPARATOR) { upperCase = true; } else if (upperCase) { sb.append(Character.toUpperCase(c)); upperCase = false; } else { sb.append(c); } } return sb.toString(); }  static String toCamelCase(String s); static String toCapitalizeCamelCase(String s); static String getIp(HttpServletRequest request); static String getCityInfo(String ip); static String getHttpCityInfo(String ip); static String getLocalCityInfo(String ip); static String getBrowser(HttpServletRequest request); static String getWeekDay(); static String getLocalIp();  }### Answer:
@Test public void testToCamelCase() { assertNull(toCamelCase(null)); }