Why do we use Map.Entry ?

Question

I have this example of mine where am able to do everything using the entrySet() method, hence I dont see any use of Map.Entry.
public class HashMapDemo {
     public static void main ( String args [])
                  HashMap hm = new HashMap();
                  hm.put("Rohit", new Double(3434.34));
                  hm.put("Rohita", new Double(3435.34));
                 hm.put("Mohit", new Double(123.22));
                 hm.put("Ashish", new Double(1200.34));
                 hm.put("Khariwal", new Double(99.34));
                 hm.put("Pankaj", new Double(-19.34));
                 Set set = hm.entrySet();
                   System.out.println("the value of set is " + set);
                   Iterator i = set.iterator();          
                   while (i.hasNext())
System.out.println(i.next());
         }

Answer 1

jose_an wrote:
What i exactly meant to ask is what's the exact need of Map.Entry inner class in HashMap.
If we can use an iterator then whats the need for Map.EntryYou can iterate over the keys, if all you want is the keys.
You can iterate over the values, if all you want is the values.
You can iterate over the key/value pairs, if you want to process all the pairs.
Map.Entry is not strictly necessary--or at least doesn't need to be made public--but it can be useful. Sure, you could just use keySet() instead of entrySet() and then use each key to get the corresponding value, but if you want to work with both together, it can make for clearer code to have a single object that represents that pairing.
Also, when iterating over a map's key/value pairs, it could be somewhat faster to just iterate over the entrySet, rather than iterating over the keys and then calling get() each time. In most cases, the difference should be negligible, but depending on the map implementation and usage profile, it could be significant.