void readUserListIfNeeded() throws IOException {

		long lastMod = userFile.lastModified();
		if (lastUserListChange == lastMod) {
			if (lastMod == 0) {
				// Create empty file if it does not yet exist
				writeUserList();
			}
			return;
		}

		LinkedHashMap<String, UserEntry> list = new LinkedHashMap<>();
		HashMap<X500Principal, UserEntry> lookupMap = new HashMap<>();

		readUserList(userFile, list, lookupMap);

		userList = list;
		dnLookupMap = lookupMap;
		lastUserListChange = lastMod;
	}
Read user data from file if the timestamp on the file has changed.

@throws IOException if error occurs while updating user file
Ghidra/Features/GhidraServer/src/main/java/ghidra/server/UserManager.java