Using-concurrenthashmap-efficiently

Iterate through all the keys in the hashmap and do some operation on its value(read only operations). Don't iterate over the key set to then retrieve the values too - iterate over the entry set directly: for (Map.Entry<String, float[]> e : map.entrySet() { String key = e.getKey(); float[] value = e.getValue(); //do something with them } This is more efficient in general (even for "normal" HashMaps), but it will also reduce contention in your case (half as many accesses to the map). Add new key,value pairs in the Hashmap. Yes it is simply: map.put(s, f); Remove Certain keys from the Hashmap. If you need to check that the key contains a given substring then you do need to iterate over the keys like you are doing, although I'm not sure why you have a while+for+break instead of a simple for.

source: http://stackoverflow.com/questions/18555506/using-concurrenthashmap-efficiently