I want execute a .jar with arguments from NSIS, like java -jar -Xmx1024M myjava.jar . But I don`t know how. Is this possible?
Executing a .jar directly might not make that much sense in a installer but you can take the code from a simple NSIS Java launcher and use it in the installer if you only need to run this Java application once.
If the user is going to run it multiple times then it makes more sense to use a real Java launcher like Launch4j or one of the many other Java launchers out there.