DaemonUmbra

In the place you did before, but this time before typing the java command, type cd Downloads (cd = Change Directory)

Yes, and remove any files you put in there

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Don't put any files in there, ever. The person who told you to do that is an idiot and a ban evader. Looking back I'm fairly certain your issue what you hadn't navigated into your downloads folder before running the command, so java was trying to find the installer in your user folder. Look up the cd command.

Please provide screenshots of where the installer is, showing the file explorer's address bar and cmd showing your command and response

Without the angle brackets, and include the .jar file extension

Provide a screenshot of the command window showing what you typed and the response

There are two readString methods, one takes an argument the other doesn't. The no-arg one you're using is only present on the client.

What happens if you open a command prompt, navigate to the folder the jar file is in, and run the command java -jar <jar name>?

What did JarFix say this time?

The two are not tied together in any way. Settings -> Apps & Features -> Search "Java" -> Uninstall any that aren't 64-bit Oh WIndows 7... just remove the one that doesn't say 64-bit

Uninstall the 32-Bit and run JarFix again

User was banned for piracy. Buy the game.

Where did you get the mod from? Can you provide screenshots of the mod in the folder?

Is this what you did?

Please provide logs/debug.log using one of the sites listed in the "Logs" section of my signature below

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

How did you import the project? Did you run gradlew eclipse and import it as an eclipse project or did you import the folder as an existing gradle project?

Refresh the project

Read the mod page for Dark Utilities, it requires a library mod you don't have. Also report to them that they aren't properly indicating the dependency in their mods.toml, preventing Forge from showing an error screen.

mod or mods?

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

Try removing Optifine and OptiForge. If that doesn't work then provide logs/debug.log

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.