Unable To Make Custom Minecraft Version Without It Redownloading Or Deleting The .jar File. All I tried to load was changing the byte of the biome array list from byte to integer. it's ahu.class and it wouldn't load for nothing because, it just redownloaded the freaken .jar file. I remember loading cubic chunks and they had base class edits what is going on here. I have tried renaming everything. I have tried editing the version's .json file. I have tried using multi mc and technic launcher they all do the same thing. I just wanted to play modded biomes is that so hard to ask. Why does it keep resetting the data?
You have to edit the json to remove the references to the downloads for the jar, which is located near the end of the file, as shown in this example for 1.8.8 (the version doesn't matter); delete everything that is highlighted in green (except for the assets line) the right so it looks like the left. Make sure that you delete the comma at the end of the assets line and the brackets match up or the launcher won't parse the file correctly:
Most other mods get around this by using an installer; unfortunately, I do not know of any generic mod installer that can be used to install mods into the jar (ideally, as simple as adding class files to a folder along with the installer, then the user downloads and runs the installer which then lets them install it into a profile, just like Optifine or Forge).
There is another method that I used before when I used Forge; I added Optifine as a library (back then it was not fully Forge compatible) and did the same for a personal mod (I only used Forge for a few Forge mods); what I did was zip up the classes and rename the zip folder to a jar file (conveniently, they are the same thing with different extensions) and edited the json to include it as a library; this has the advantage of not modifying the game until runtime so the launcher can't overwrite the jar. Note that I have not tested this recently but my 1.6.2 Forge installation still launches normally (the json file it uses still uses the original format, without the downloads that were added this past February but the launcher should not replace a modified json):
As seen here the "jar" is just a bunch of classes; trying to run it gives me "invalid or corrupt jar file" but it works as a library:
Part of the json file (I just modified the default Forge json):