Add and Retrieve data from HashMap in Java

package collections;

import java.util.HashMap;
import java.util.Map;

public class AddRetUsingMap {

Map<Integer,String> m=new HashMap<Integer,String>();
public void addData()
{
m.put(1,"Abhishek");
m.put(2,"Abhinav");
m.put(3,"Alok");
m.put(4,"Abhijeet");
}
public void retData()
{
//retrieve data using  for-each loop
for(Map.Entry<Integer,String> entry:m.entrySet() )
{
System.out.println("RollNo["+entry.getKey()+"],Name["+entry.getValue()+"]");
}
}
public static void main(String[] args) {

AddRetUsingMap am=new AddRetUsingMap();
//call method to add the data into hashmap
am.addData();
//call method to display the stored data
System.out.println("List of Roll Numbers and Students: ");
am.retData();

}

}