Main Difference between TreeMap and TreeSet is that TreeMap is implementation of Map interface while TreeSet is implementation of Set interface. There are some similarities between both TreeMap and TreeSet and few differences as well. In this Java tutorial we will first see similarities between TreeMap and TreeSet and than we will see differences between TreeMap and TreeSet in Java. Key point to remember about TreeMap and TreeSet is that they use compareTo() or compare() method to compare object, So if uses puts a String object in TreeSet of Integers, add() method will throw ClassCastException at runtime prior to Java 5, with Java 5 you can use Generics to avoid this happening by declaring TreeMap and TreeSet with parametrized version.
Here is a list of similarities between TreeMap and TreeSet in Java: