Installing Java application

I am looking for a simple and reliable freeware mechanism to install Java application on different platforms (Windows, Linux, MacOS). The IzPack that I found is a fine tool but it presumes that Java is already installed on the target system. In my case that is not always the truth.

Is there any simple and platform-independent mechanism that would install JRE (if necessary) and then run a Java installation software?

Thanks!

Installers have been discussed several times on this forum, I suggest you search the forum or just google for Java Installers and see what is available.