I have a fat client application which looks up fairly static reference
data (database table)

Example - columns to display for a search result list

I have the following code below as a snippet to cache the results while
the application is running - restarting the app clears the cache.

However it looks fragile and relies on the developer not making a
mistake when assigning the key for the cached service call

Is there a design pattern best suited for this common issue?

private static Hashtable cache = new Hashtable();

public static AppColumnList getSearchColumns(int applicationId) {
   String key = applicationId + ":ServiceClass:getSearchColumns";
   if (cache.containsKey(key)) {
       AppColumnList value = (AppColumnList) cache.get(key);
       return value;
   } else {
       AppColumnList value = getService().getAppColumns(applicationId,
userid);
       cache.put(key,value);
       return value;
   }
}