• Duplicate objects not allowed.
  • Do not maintain insertion order.
  • Heterogeneous object are not allowed (it will throw class cast exception)
  • Null not allowed.
  • it creates an internal tree of the link list.
  • if we are inserting null in a nonempty tree set then it will throw a null pointer exception.
  • if we insert null in empty TreeSet then it will accept data.
  • if we are inserting the first null in empty tree set and then we are inserting another element then we will get null pointer exception
  • before 1.6 v null was allowed as the first element in empty TreeSet.
  • In TreeSet we can insert only Homogeneous and Comparable objects only , otherwise it will throw class cast exception.