Repeated Key algorithm obtained from net can't detect user class keys?

[Jacky Luk]

Map<Unit.PathPoint2, Integer> occurrencies = new HashMap<Unit.PathPoint2, Integer>();
for (Unit.PathPoint2 word : blockedTiles) {
      occurrencies.put(word, occurrencies.containsKey(word)
             ? occurrencies.get(word) + 1 : 1);
}
for (Entry<Unit.PathPoint2, Integer> entry : occurrencies.entrySet()) {
   System.out.println("PathPoint: "+ entry.getKey().x + " " + entry.getKey().z + 
            " " + ", occurences: "+ entry.getValue());
}        

All occurrencies happen to be one only no matter they have repeated several times.
Any ideas why?
Thanks
Jack

[Tushar Goel]

Hashmap stores the key by calculating hashes. For same key hash always same so it always getting replaces your old entry with the new entry.

[Jacky Luk]

Hello there,
I have changed to String as keys, and it works well.
But I've got a new question.
How do I design the algorithm such as the following happens

0:1:1
0:1:1 - clashed
0:1:2 - not clashed
1:1:1 - not clashed
2:1:1 - not clashed

I can use a SortedSet for that, but now I want to count how many occurrencies happen
for 1:1, 1:2 etc after the Set has been filtered. (The second and the third keys)
How can I do that?
Thanks
Jack

[Campbell Ritchie]

You cannot expect a hash map to work unless the “K”s are immutable, with correctly‑overridden equals() and hashCode() methods. Does your path point class fulfil those requirements?

[Stephan van Hulst]

You should use a strong type for your key and not a String. You should implement the equals() and hashCode() methods on your key type properly. Please make your key type immutable. If you're using Java 8, you can use Map.merge() to add entries to a map, and handle the situation where the entry already exists graciously: occurences.merge(word, 1, (a,b) -> a+b);