What happens to the lookup in a Hashmap or Hashset when the objects Hashcode changes

Question

In a Hashmap the hash code of the key provided is used to place the value in the hashtable. In a Hashset the obects hashcode is used to place the value in the underlying has

Answer 1

The HashSet is backed up by a HashMap.

From the javadocs.

This class implements the Set interface, backed by a hash table (actually a HashMap instance).

So if you change the hashcode, I doubt whether you can access the object.

Internal Implementation Details

The add implementation of HashSet is

 public boolean add(E e) {
        return map.put(e, PRESENT)==null;
 }

The key is the elem and value is just a dummy Object called PRESENT

and the contains implementation is

public boolean contains(Object o) {
        return map.containsKey(o);
}