Java HashMap basic operations - get value, update value, contains value and loop through hashmap

HashMapDemo.java

// Java HashMap basic operations - get value, update value, contains value and loop through hashmap
import java.util.*;
 
class demo
{
    public static void main(String[] args)
    {
        Integer[] a = new Integer[]{1,2,3,1,2,4,5,6,2,3};
        Map<Integer, Integer> dataSet = new HashMap<Integer, Integer>();
        int length = a.length;
        int value  = 0;
        
        for(int i=0; i<length; i++)
        {
            if (dataSet.containsKey(a[i]))
            {
                value = dataSet.get(a[i]);
                value++;
                dataSet.put(a[i], value);
            }
            else
            {
                dataSet.put(a[i], 1);
            }
        }
        
        for (Map.Entry<Integer,Integer> entry: dataSet.entrySet())
        {
           System.out.println(" Key " + entry.getKey() + " Value " + entry.getValue() + "   ");
        }   
    }
}