You will need Java to run the collectors. Unless I'm misunderstanding you can check the installed programs in your control panel to see if and what version of Java is installed.
I'm not sure what you are referring to by "plugin dashboard." A collector must be installed in order to run a plugin as a monitor from a collector, but a monitor can be run against any host - they don't need a collector for that if that is what you are asking.
For Windows you do not need to have Java installed. the msi used to install the components does not require java and the components come with a bundled java 1.8 64-bit.
For Linux you need java to install the server components. Once they are installed the processes will use the bundled java.
See system requirements for more info:
As for your issues with the plugin dashboard: I see that you in another comment wrote "Data power plugin". Do you get any errors in the collector logs when it stops working? Does it start working again if you stop and restart the monitor?
As @Michael L. said that it bundles with the installer for windows component, therefor, we don't need to install as prerequisites.
You can use the java -version command on the command prompt to check the version and result could be similar as below: