Question

So because Javolution does not work (see here) I am in deep need of a Java Map implementation that is efficient and produces no garbage under simple usage. java.util.Map will produce garbage as you add and remove keys. I checked Trove and Guava but it does not look they have Set<E> implementations. Where can I find a simple and efficient alternative for java.util.Map?

Edit for EJP:

An entry object is allocated when you add an entry, and released to GC when you remove it. 🙁

   void addEntry(int hash, K key, V value, int bucketIndex) {
        Entry<K,V> e = table[bucketIndex];
        table[bucketIndex] = new Entry<K,V>(hash, key, value, e);
        if (size++ >= threshold)
            resize(2 * table.length);
    }

Answer 1

One option is to try to fix the HashMap implementation to use a pool of entries. I have done that. 🙂 There are also other optimizations for speed you can do there. I agree with you: that issue with Javolution FastMap is mind-boggling. 🙁