Documentation for searchV2(String query) how to type a query ?

I have been using older dropboxapiv2 (java) to search "Files" for 2 years. Today it started to malfunction due to a dropbox server side "malformed query" error. While I assume it is again a Dropbox development malfunction, I also would like to upgrade the dropboxapiv2 I am using to version 3.1.3 . It seems there is now a search method searchV2(String query) ,but I could not find any documentation about how to write a search query for dropbox search in api. 

Can anybody help ?

with errors below is my code for, now deprecated, search method

public List<SearchMatch> findFile(String code) {
	try {
		SearchResult sr = dbxClient.files().search("/drawings/",code);
		List<SearchMatch> sm = sr.getMatches();
		List<SearchMatch> rmlist = new ArrayList<SearchMatch>();
		for (SearchMatch searchMatch : sm) {
			if (!fileMidir(searchMatch.getMetadata())) {
				rmlist.add(searchMatch);
			}
		}
		for (SearchMatch searchMatch : rmlist) {
			sm.remove(searchMatch);
		}
		
		return sm;
		
	} catch (DbxException e) {
		e.printStackTrace();
	}
	return null;
}
public boolean fileMidir(Metadata metadata){
	if (metadata instanceof FolderMetadata) {
		return false;
	}else {
		return true;
	}
}