before: get = 100, contains = true

after acc.owner = "ankur":
map.get(acc)             = null
set.contains(acc)        = false
map.containsKey(acc)     = false
map.size()               = 1
iteration still sees it  = [Account(ankur)]
map.remove(acc)          = null
map.size() after remove  = 1

set.add(acc) again -> size = 2 [Account(ankur), Account(ankur)]  (one object, two entries)

immutable key: map.get("asha") = 1