Question

I want to display the values in a HashMap. A HashMap may have duplicate values (but not duplicate keys), but I want to display a value only once.

So I should find whether the Map has duplicate values. I know we can iterate over the Map and use the return boolean of map.containsValue(value). I want to know whether any method exists to find duplicate values in map or we should I write code myself?

Answer 1

A simple solution would be to compare the size of your values list with your values set.

// pseudo-code
List<T> valuesList = map.values();
Set<T> valuesSet = new HashSet<T>(map.values);
// check size of both collections; if unequal, you have duplicates