public boolean hasShutdownHook(final Runnable shutdownHook) {
        return hooks.contains(new HookEntry(shutdownHook, 0));
    }
Indicates if a shutdownHook is registered or not.

@param shutdownHook shutdownHook to check if registered.
@return TRUE/FALSE depending if the shutdownHook is is registered.
shenyu-client/shenyu-client-core/src/main/java/org/apache/shenyu/client/core/shutdown/ShutdownHookManager.java