Return from the logger manager singleton's category registry the address of the non‐modifiable category having the specified categoryName, or, if no such category exists, add a new category having categoryName to the registry if possible (i.e., if the registry has sufficient capacity to accommodate new entries); otherwise, return the address of the non‐modifiable Default Category. If the logger manager singleton is not initialized, return 0 with no effect. If a new category is created, it will have the same threshold levels as the category in the logger manager singleton whose name is the longest non‐empty prefix of categoryName if such a category exists, and the threshold levels will be set as if setCategory had been called otherwise.