public static synchronized ResourceReaper instance() {
        if (instance == null) {
            boolean useRyuk = !Boolean.parseBoolean(System.getenv("TESTCONTAINERS_RYUK_DISABLED"));
            if (useRyuk) {
                //noinspection deprecation
                instance = new RyukResourceReaper();
            } else {
                String ryukDisabledMessage =
                    "\n" +
                    "********************************************************************************" +
                    "\n" +
                    "Ryuk has been disabled. This can cause unexpected behavior in your environment." +
                    "\n" +
                    "********************************************************************************";
                LOGGER.warn(ryukDisabledMessage);

                instance = new JVMHookResourceReaper();
            }
        }

        return instance;
    }
Internal constructor to avoid custom implementations
core/src/main/java/org/testcontainers/utility/ResourceReaper.java