Using an instance of an object as a key in hashmap, and then access it with exactly new object? [duplicate]

Question

I have a hasmap with a key object,

HashMap<Key, Object> test; 

and make new Key("the same") as key..

so its like..:

test.put(new Key("the same"), someObject); 

(without storing that key in a variable)

so.. after a while... i want to access the hashmap, because i do not have the object, i've tried to make new Key("the same") and make it as a key. But it didnt work.

How to make it work? (without saving the first object "key" in a variable)

So meanwhile, for now, im using String object as a key.

HashMap<String, Object> 

Answer 1

You need to implement hashCode and equals on Key. The default implementation of these methods simply checks for instance equality (in other words, two Objects will only be equal if they are in fact the same object).

Further reading

Effective Java - Methods common to all objects