Is there any way to dynamically compile java code at runtime

Question

So im trying to make my own game engine and I am trying to figure out is there any way to compile java code while running it? If so how do you do it.

example:

While im running the code and I make changes to it I want it to also change whats happening on the game window I know you can do something like this in c/c++ but I dont know how to do it in java.

what I mean is can I recompile java code while im running it @lulle — ImmanuelC, May 10 '21 at 22:23
You can not "compile it", but you can generate bytecode in runtime. https://stackoverflow.com/q/4016305/9978153 — Vladimir Shefer, May 10 '21 at 22:25
IDEs like Eclipse and IntelliJ can let you update code while it's running. — khelwood, May 10 '21 at 22:28
[Remote debugging a Java application](https://stackoverflow.com/q/975271/2970947) should be enough to get you started. — Elliott Frisch, May 10 '21 at 22:29
JRebel is one option: https://www.jrebel.com/products/jrebel — Jeff Scott Brown, May 10 '21 at 22:41
@VladimirShefer "You can not compile it" - It is not correct that you cannot compile Java code while it is running. You can indeed. We do it all the time. — Jeff Scott Brown, May 10 '21 at 22:42
thanks! @JeffScottBrown but I have one problem its a paid software and im looking for something free — ImmanuelC, May 10 '21 at 22:45
@lulle - Compilation is required before the code changes can be reflected in the running app. — Jeff Scott Brown, May 10 '21 at 22:55
@ImmanuelC Spring Loaded (https://github.com/spring-projects/spring-loaded) is another option, and it is free. — Jeff Scott Brown, May 10 '21 at 22:55
Yes that is possible. But do you want it only while you develop and debug your game, or do you want your game to ship with the option that the end user can write java which then get run in your app? Both are possible for the method to do them differ a lot. — MTilsted, May 10 '21 at 22:56
@lulle it is easier to develop games that way and other game engine like unity, unreal, godot they all allow you to compile the game engine and the code you had written without closing the application. — ImmanuelC, May 10 '21 at 22:57
@MTilsted I want to compile the code while its running for convenience and I am not creating a game I am creating a game engine so others can build there games on top of my engine. — ImmanuelC, May 10 '21 at 23:04

score 1 · Answer 1 · answered May 10 '21 at 23:08

1

You can do it with https://dcevm.github.io/

It is a full jre and easy to use. All you have to do is configure your ide(Eclipse or whatever you use to use the dcevm as jre).

It will then pickup all your changes. So if you use it with eclipse it will pickup the change each time you save a file in eclipse, since eclipse compiles on save.

answered May 10 '21 at 23:08

MTilsted

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I cant get it too work with intellij – ImmanuelC May 10 '21 at 23:28
When I compile the code in intellij nothing happens on the window – ImmanuelC May 10 '21 at 23:31
@ImmanuelC Try starting with a simple test. Have a loop which just prints (With System.out.println("Hello world"), then run it and then change the code to print something else. That will tell you if the code gets reloaded depending on if the printed text changes. – MTilsted May 10 '21 at 23:44
alright thanks! – ImmanuelC May 10 '21 at 23:46
I still can't get it to work :( – ImmanuelC May 10 '21 at 23:51
thanks for you help anyways – ImmanuelC May 10 '21 at 23:55

Is there any way to dynamically compile java code at runtime

1 Answers1