What is the differences between HashMap and HashTable in Java

HashMap and HashTable both are one of the most important classes of Java Collection framework. Both HashMap and HashTable stores the data in key value pair and at the time storing data hashing is used to hash the key and the resulting hash code is used as the index at which the value is stored within the table. But still, there are many differences between both these classes which we would discuss below.

The following are the important differences between HashMap and HashTable.

Example of HashMap vs HashTable

JavaTester.java

import java.util.*;
import java.lang.*;
import java.io.*;
public class JavaTester{
   public static void main(String args[]){
      Hashtable ht=new Hashtable();
      ht.put(101,"John");
      ht.put(101,"Jhony");
      ht.put(102,"Smith");
      ht.put(103,"Andy");
      System.out.println("-------------Hash table--------------");
      Set<Integer> keySet = ht.keySet();
      for (Integer key:keySet) {
         System.out.println(key + " "+ht.get(key));
      }
      HashMap hm=new HashMap();
      hm.put(100,"John");
      hm.put(104,"John"); // hash map allows duplicate values
      hm.put(101,"Smith");
      hm.put(102,"Andy");
      System.out.println("-----------Hash map-----------");
      Set<Integer> keySet1 = ht.keySet();
      for (Integer key:keySet) {
         System.out.println(key + " "+hm.get(key));
      }
   }
}

Output

-------------Hash table--------------
103 Andy
102 Smith
101 Jhony
-----------Hash map-----------
100 John
101 Smith
102 Andy
104 John