Difference between TreeMap and TreeSet in Java

Main Difference between TreeMap and TreeSet is that TreeMap is implementation of Map interface while TreeSet is implementation of Setinterface. There are some similarities between both TreeMap andTreeSet 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() orcompare() method to compare object, So if uses puts a String object inTreeSet 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.

Similarities between TreeMap and TreeSet in Java
Here is a list of similarities between TreeMap and TreeSet in Java:

1) Both TreeMap and TreeSet are Sorted Collection which means they keep there element in predefined Sorted order. Sorting order can be natural sorting order defined by Comparable interface or custom sorting Order defined by Comparator interface. Both TreeMap and TreeSet has overloaded constructor which accept a Comparator, if provided all elements inside TreeSet or TreeMap will be compared and Sorted using this Comparator.

2) TreeSet is practically implemented using TreeMap instance, similarly like HashSet is backed by HashMap instance.

3) Both TreeSet and TreeMap implements Collection interface so they can be passed to method where a Collection is accepted.

4) Both TreeMap and TreeSet are non synchronized Collection, hence can not be shared between multiple threads. You can make both TreeSet and TreeMap synchronized by wrapping them into Synchronized collection by callingCollections.synchroinzedMap() method.

5) Iterator returned by TreeMap and TreeSet are fail-fast, means they will throw ConcurrentModificationException when TreeMap orTreeSet is modified structurally once Iterator is created. this fail-fast behavior is not guaranteed but works in best effort.

6) Both TreeMap and TreeSet are slower than there Hash counter part like HashSet and HashMap and instead of providing constant time performance for add, remove and get operation they provide performance in O(log(n)) order.

TreeSet vs TreeMap in Java

Now let's see some differences between TreeSet vs TreeMap in Java:

1) Major difference between TreeSet and TreeMap is that TreeSet implements Set interface while TreeMap implements Map interface in Java.

2) Second difference between TreeMap and TreeSet is the way they store objects. TreeSet stores only one object while TreeMap uses two objects called key and Value. Objects in TreeSet are sorted while keys in TreeMap remain in sorted Order.

3) Third difference between TreeSet and TreeMap is that, former implements NavigableSet while later implementsNavigableMap in Java.

4) Fourth difference is that duplicate objects are not allowed in TreeSet but duplicates values are allowed in TreeMap.

That's all on difference between TreeSet and TreeMap in Java. if you find any other significant difference between TreeMap andTreeSet then please post as comment.