Question

I read that HashTable can map same key to multiple values. That’s what collision is.

Now I run the program like this:

Dictionary<String,String> hTable = new Hashtable<String,String>();
hTable.put("a", "aa");
hTable.put("a", "ab");
System.out.println(""+hTable.get("a"));

My thinking says I should get aa and ab.

But actual output is ab

Why is it so? Where is the collision then?

Answer 1

There is no collision. A HashTable entry maps a key to only one value.

The third line in your sample:

hTable.put("a", "ab");

replaces the mapping from a to aa with a mapping from a to ab.

After your four lines of code complete execution, hTable has only one mapping: a to ab.