Does adding a duplicate value to a HashSet/HashMap replace the previous value

Question

Please consider the below piece of code:

HashSet hs = new HashSet();
hs.add(\"hi\"); -- (1)
hs.add(\"hi\"); -- (2)

hs.size() w

Answer 1

You need to check put method in Hash map first as HashSet is backed up by HashMap

1. When you add duplicate value say a String "One" into HashSet,
2. An entry ("one", PRESENT) will get inserted into Hashmap(for all the values added into set, the value will be "PRESENT" which if of type Object)
3. Hashmap adds the entry into Map and returns the value, which is in this case "PRESENT" or null if Entry is not there.
4. Hashset's add method then returns true if the returned value from Hashmap equals null otherwise false which means an entry already exists...