TreeSet in Java In this article, we are going to learn about what is TreeSet in Java. Also, we look at the upper hierarchy of TreeSet in Java. We will look at the methods provided by TreeSet. Content of the Article What is TreeSet in Java? Hierarchy of the TreeSet in java? How to create an object of TreeSet in java? How to add elements to the TreeSet in java? How to iterate TreeSet in java? How to check whether an element is stored in the TreeSet in Java? How to remove elements from the TreeSet in java? Reverse order set provided by the TreeSet in Java? How to get sub-set from the TreeSet in Java? How to get first and last element from the TreeSet in Java? Few more methods of TreeSet in java What is TreeSet in Java? TreeSet in java is an implementation of Set interface i.e., duplicate elements are not allowed , Set interface provides the facility to store and retrieve elements. TreeSet internally maintains a TreeMap as its internal data structure, so