Replacing a HashSet Java member

Question

I have Set of that structure. I do not have duplicates but when I call: set.add(element) -> and there is already exact element I would like the old to be replac

Answer 1

Check the HashSet code within the JDK. When an element is added and is a duplicate, the old value is replaced. Folk think that the new element is discarded, it's wrong. So, you need no additional code in your case.

UPDATED---------------------

I re-read the code in JDK, and admit a mistake that I've made.

When put is made, the VALUE is replaced not the KEY from an HashMap.

Why am I talking about Hashmap??!! Because if you look at the HashSet code, you will notice:

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

So the PRESENT value is replaced with the new one as shown in this portion of code:

      public V put(K key, V value) {
        if (key == null)
            return putForNullKey(value);
        int hash = hash(key);
        int i = indexFor(hash, table.length);
        for (Entry e = table[i]; e != null; e = e.next) {
            Object k;
            if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
                V oldValue = e.value;
                e.value = value;
                e.recordAccess(this);
                return oldValue;
            }
        }

        modCount++;
        addEntry(hash, key, value, i);
        return null;
    }

But I agree, the key isn't replaced, and since the keys represent the HashSet's values, this one is said to be "untouched".