String null to empty

You can use Objects.toString() (standard in Java 7):

Objects.toString(gearBox, "")

Objects.toString(id, "")

or 

StringUtils.defaultString(String str)

Returns either the passed in String, or if the String is null, an empty String ("").

 StringUtils.defaultString(null)  = ""
 StringUtils.defaultString("")    = ""
 StringUtils.defaultString("bat") = "bat"