In my project, the jar file itself is 20MB, and the resulting files generated by javapackager are: 55MB (.exe), 90MB (.dmg), and 67MB (.deb), all of which include the jar file inside them. These are not the total file size after installation, though.

Was this using the "javapackager" tool? This seems to have been introduced in Java 1.7 as far as I can tell.

Yes, I mentioned javapackager in the comment.

Hmm, indeed it does, but I could have swore that the first time I read the comment it didn't. I guess I forgot how to read earlier :-)

Yes in Java 8 it's comparable. In 9 it should be smaller due to some dead code elimination on module boundaries, but 9 just came out so it's a bit early for people to have experience with it yet.

Note that even in 8 you can do a DCE pass over the code and erase files you know you won't need from the JRE image by hand. I did this and shrank the size of the download by about half. The JavaScript world calls this "tree shaking", you can use ProGuard to do it in Java but it's a bit fiddly to set up.

For Java 8 it is about 200mb. Java 9 should be smaller because it should only bundle the parts the app actually used.

Isn’t that the JDK, the jre is smaller from what I remember.