Get Set view of Keys from Java HashMap example

/*
  Get Set view of Keys from Java HashMap example
  This Java Example shows how to get a Set of keys contained in HashMap
  using keySet method of Java HashMap class.
*/
 
import java.util.Iterator;
import java.util.HashMap;
import java.util.Set;
 
public class GetSetViewOfKeysFromHashMapExample {
 
  public static void main(String[] args) {
 
    //create HashMap object
    HashMap hMap = new HashMap();
 
    //add key value pairs to HashMap
    hMap.put("1","One");
    hMap.put("2","Two");
    hMap.put("3","Three");
 
    /*
      get Set of keys contained in HashMap using
      Set keySet() method of HashMap class
    */
 
    Set st = hMap.keySet();
 
    System.out.println("Set created from HashMap Keys contains :");
    //iterate through the Set of keys
    Iterator itr = st.iterator();
    while(itr.hasNext())
      System.out.println(itr.next());
 
    /*
       Please note that resultant Set object is backed by the HashMap.
       Any key that is removed from Set will also be removed from
       original HashMap object. The same is not the case with the element
       addition.
    */
 
    //remove 2 from Set
    st.remove("2");
 
    //check if original HashMap still contains 2
    boolean blnExists = hMap.containsKey("2");
    System.out.println("Does HashMap contain 2 ? " + blnExists);
  }
}
 
/*
Output would be
Set created from HashMap Keys contains :
3
2
1
Does HashMap contain 2 ? false
*/