I need to develop a few Node-RED flows, but don't want to expose the flow diagrams on UI to the users rather I need to trigger the created flows using any kind of language like Javascript/Node JS/ Java.
Please let me know if there is any way of doing this.
What do you mean "trigger those flows". Trigger what exactly.
There are many ways of triggering parts of a node red flow, inject node, Cron schedule, MQTT, UDP, TCP, rest , http you name it. And each of this can be triggered by Java, .net, PHP, cobal, python etc if you want it to.
It is fairly much a case of if you can think it, you can do it.
Indeed. How do you want to "trigger". There are plenty of examples of triggering Node-RED flows with web apps, physical buttons, commercial home automation or IoT devices, sensors (temperature, humidity, pressure, light, ...) and so much more.