JAR installer that auto-detects if Java is there and autostarts the application

Question

I need to build an installer that does the following:

1. Installs my jar on the client.
2. Auto-detects if JRE is installed (in which case it does not re-in

Answer 1

Commercial tools like InstallAnywhere can do that. After installing the JAR (and links and such), installers can check the registry if Java is already installed and proceed or not. As long as the installer supports all needed plattforms, you are fine.