[Cdk-devel] [Request for Comments]: ChemObject Properties

[John M. <jo...@eb...>]

Hi All,

I found two questions regarding this current code from IChemObject. They aren't bugs but it would be useful to have opinions.

if (properties == null)
    properties = new LinkedHashMap<Object, Object>();
return properties;

https://gist.github.com/4107408

This code allows lazy initialisation - so every ChemObject doesn't have a map unless it needs it. However it is not thread safe - it is very possible to have one thread put properties into a map which is then replaced by a different map. Also LinkedHashMap takes more memory then a normal HashMap as there is a double linked list running through the entires. 

1. should lazy initialisation be thread safe? There is a pattern to do this which minimises the performance cost of synchronising. 
2. can LinkedHashMap be replaced with HashMap? There are very few times you want the order of insertion in a map, currently properties are predominately used as a general property store.
John May | Predoctoral Student – Chemoinformatics and Metabolism 
European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SD, UK 
jo...@eb... | +44–(0) 1223 49 2603