java - HashMap.containsValue - What's the point?

Question

I've got a HashMap and I need to fetch an item by its integer value. I notice there's a containsValue() function, but it would appear I still have to iterate through the map to find the correct index anyway.

My question is; why use containsValue() if I'm required to traverse it afterwards?

Also, am I missing the point completely? ;-)

Answer 1

A map maps a key to a value. If you have a value and you know the map contains this value, why do you need the key anymore?

On the other hand, if you really need the key or you have just a property of the value, you can iterate the entrySet(), check the value and return the key if found:

for (Map.Entry<Index,Value> entry : map.entrySet()) {
  if (entry.getValue().getXy().equals(xy)) {
    return entry.getKey();
  }
}