code: private void putForCreate(K key, V value)
          throws java.io.StreamCorruptedException
      {
          Object k = maskNull(key);
          Object[] tab = table;
          int len = tab.length;
          int i = hash(k, len);
  
          Object item;
          while ( (item = tab[i]) != null) {
              if (item == k)
                  throw new java.io.StreamCorruptedException();
              i = nextKeyIndex(i, len);
          }
          tab[i] = k;
          tab[i + 1] = value;
      }
docs: The put method for readObject.  It does not resize the table,
  update modCount, etc.