[java] How to initialize java.util.date to empty

An instance of Date always represents a date and cannot be empty. You can use a null value of date2 to represent "there is no date". You will have to check for null whenever you use date2 to avoid a NullPointerException, like when rendering your page:

if (date2 != null)
  // print date2
else
  // print nothing, or a default value