The TreeMap Class implements the Map Interface of the java collection framework . The TreeMapstores the element in the tree like structure. TreeMap does not provide synchronization but allows to provide “Null” Keys and “Null” Values .

The TreeMap uses initial capacity and load factor as parameters. The initial capacity determines the number of buckets in the hash table whereas load factor determines how to retrieve hash table before its initial capacity is increased. When the hash table reaches to its full capacity, then it is rehashed, means the internal data structures are re-built and it doubles the buckets in the hash table. The HashMap initial default capacity of is 16 with a load factor of 0.75.

TreeMap Class in Java Collection

The HashSet Interface class Hierarchy is given below

java.lang.Object
-> java.util.AbstractMap<K,V>
->-> java.util.TreeMap<K,V>

The implemented interfaces by HashMap Interface:

Serializable, Cloneable, Map <K,V>

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

The HashSet Interface provides the below given constructors

Methods of HashMap Interface

The HashMap Class implements the Map Interface of the java collection framework . The HashMap stores the element Key-Value pair in the hash table. HashMap does not provide synchronization but allows to provide “Null” Keys and “Null” Values .

The HashMap uses initial capacity and load factor as parameters. The initial capacity determines the number of buckets in the hash table whereas load factor determines how to retrieve hash table before its initial capacity is increased. When the hash table reaches to its full capacity, then it is rehashed, means the internal data structures are re-built and it doubles the buckets in the hash table. The HashMap initial default capacity of is 16 with a load factor of 0.75.

HashMap Class in Java Collection

The HashMap class Hierarchy is given below

java.lang.Object
-> java.util.AbstractMap<K,V>
->-> java.util.HashMap<K,V>

The implemented interfaces by HashMap Interface:

Serializable, Cloneable, Map <K,V>

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

The HashSet Interface provides the below given constructors

Methods of HashMap Interface

HashMap Example in Java Collection

package core.java.planforexams;
import java.util.HashMap;
import java.util.Map;
public class BasicHashMapExample {
	public static void main(String args[]){  
	// HashMap Object with student names
	HashMap<Integer,String> students=new HashMap<Integer,String>();//Creating HashMap    
	students.put(1,"Mohit");   
	students.put(2,"Rohit");    
	students.put(3,"Mihika");   
	students.put(4,"Khushal");   
	   System.out.println("Student HashMap Iteration...");  
	   for(Map.Entry names : students.entrySet())
	   {    
		   System.out.println(names.getKey()+" "+names.getValue());    
	   }   
	}
}
Output: 
Student HashMap Iteration...
1 Mohit
2 Rohit
3 Mihika
4 Khushal