Key with same hashcode

[Arun Chidam]

Hi Guys,

How HashMap stores key if all the added objects has same hashcode(say 1), does it maintain internal subset of Key+value as key, if so what is the data type of subset(is it stored as hashmap inside hashmap)?

Thanks,
Arun

[Luigi Plinge]

If you look at the source of HashMap

    public V get(Object key) {
        if (key == null)
            return getForNullKey();
        int hash = hash(key.hashCode());
        for (Entry<K,V> e = table[indexFor(hash, table.length)];
             e != null;
             e = e.next) {
            Object k;
            if (e.hash == hash && ((k = e.key) == key || key.equals(k)))
                return e.value;
        }
        return null;
    }

you can see that the entries are in an array of Entry objects. The for-loop just looks at each entry with the same hash until it finds one with a key that matches.

[Seetharaman Venkatasamy]

Arun Chidam wrote:How HashMap stores key if all the added objects has same hashcode(say 1)

you cant talk about adding an object in HashMap with only hashCode.you need to mention equals method also. what about equals method of all objects? if equals method of all objects are same then recent entry will replace existing and so on... else all the objects will go into one single bucket; bad programing style.

Arun Chidam wrote:
does it maintain internal subset of Key+value as key, if so what is the data type of subset(is it stored as hashmap inside hashmap)?

nope. key+value wrapped into an Object called Entry and put into an Array. the base datastructure for the Hashtable/HashMap is an array.
for more details you can view the source code of java.util.HashMap.

[Arun Chidam]

Thanks Seetharaman,Luigi

Your post cleared my doubts

Thanks,
Arun

[Seetharaman Venkatasamy]

Arun Chidam wrote:Thanks Seetharaman

You are Welcome