void (final String threadId, final String frameId, final String name) { Map<String, Set<String>> threadVars = myData.get(threadId); if (threadVars == null) myData.put(threadId, (threadVars = new HashMap<>())); Set<String> frameVars = threadVars.get(frameId); if (frameVars == null) threadVars.put(frameId, (frameVars = new HashSet<>())); frameVars.add(name); }