HashMap Vs TreeMap In Java

HsahMap:

public class HashMap<K,V>
extends AbstractMap<K,V>
implements Map<K,V>, Cloneable, Serializable

All Implemented Interfaces:
Serializable, Cloneable, Map<K,V>
Direct Known Subclasses:
LinkedHashMap, PrinterStateReasons

TreeMap:

public class TreeMap<K,V>
extends AbstractMap<K,V>
implements NavigableMap<K,V>, Cloneable, Serializable

All Implemented Interfaces:
Serializable, Cloneable, Map<K,V>, NavigableMap<K,V>, SortedMap<K,V>

public interface NavigableMap<K,V>
extends SortedMap<K,V>

Similarities between HsahMap and Synchronized

• HashMap and TreeMap both classes belong to java.util package and both are the members of the Java Collections Framework.
• HashMap and TreeMap both store key value pair as object.
• Iterator's returned by HashMap and TreeMap both are fail-fast.
• HashMap and TreeMap both uses shallow copy method to create clone of their objects.
• HashMap and TreeMap both are not thread safe means unsynchronized. 

Although we can externally create both synchronized as mention below using Collections method.

HashMap :  Map m = Collections.synchronizedMap(new HashMap (...));
TreeMap :  Map m = Collections.synchronizedSortedMap(new TreeMap (...));

Difference between HsahMap and Synchronized

HsahMap	TreeMap
HsahMap is hash table based implementation of the Map interface.	TreeMap use Red-Black tree based NavigableMap implementation which is a self-balancing Binary Search Tree.
HashMap allows a only single null key and multiple null values.	TreeMap does not allow any null keys but can have multiple null values.
HashMap is faster than TreeMap, it provides constant-time performance that is O(1) for the basic operations like get() and put().	TreeMap is slow compared to HashMap because it provides the performance of O(log(n)) for most operations like add(), remove() and contains().
HsahMap uses equals() method of the Object class to compare keys. The equals() method of Map class to overrides its values.	HsahMap uses the compareTo() method to compare keys.
HashMap has only basic functions like get(), put(), KeySet(), etc.	TreeMap has more functions like: tailMap(), firstKey(), lastKey(), pollFirstEntry(), pollLastEntry().
HashMap does not preserve insertion order. HashMap does not provide any guarantee that the element inserted.	The elements are sorted in natural order (ascending).

Related Tutorials 

• Java Collections Interview
• List Interface In Java
• ArrayList
• LinkedList
• Custom Own ArrayList Implementation
• Custom LinkedList implementation in java
• Set Interface In Java
• Map Interface In Java
• HashMap
• TreeMap
• HashMap Vs ConcurrentHashMap
• HashMap Vs HashTable In Java
• HashMap Vs HashSet In Java
• HashMap Vs TreeMap In Java
• HashMap vs LinkedHashMap In Java
• TreeSet Vs TreeMap In Java
• SortedSet Vs TreeSet In Java
• SortedMap Vs TreeMap In Java
• Array Vs ArrayList In Java
• ArrayList Vs LinkedList In Java
• How HashSet Works Internally
• How TreeMap Works Internally
• How HashMap Works Internally
• How ConcurrentHashMap Works Internally
• How To Detect Loop In A LinkedList In Java
• Detect And Remove Loop In A LinkedList