Error:

 

Execution failed for task ':compileJava'.
> Could not resolve all files for configuration ':compileClasspath'.
   > Could not find net.minecraftforge:forge:1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12.
     Searched in the following locations:
       - https://maven.minecraftforge.net/net/minecraftforge/forge/1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12/forge-1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12.pom
       - https://maven.minecraftforge.net/net/minecraftforge/forge/1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12/forge-1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12.jar
       - file:/C:/Users/burid/.gradle/caches/forge_gradle/bundeled_repo/net/minecraftforge/forge/1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12/forge-1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12.pom
       - file:/C:/Users/burid/.gradle/caches/forge_gradle/bundeled_repo/net/minecraftforge/forge/1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12/forge-1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12.jar
       - https://libraries.minecraft.net/net/minecraftforge/forge/1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12/forge-1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12.jar
       - https://repo.maven.apache.org/maven2/net/minecraftforge/forge/1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12/forge-1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12.pom
       - https://repo.maven.apache.org/maven2/net/minecraftforge/forge/1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12/forge-1.12.2-14.23.5.2859_mapped_snapshot_20171003-1.12.jar
     Required by:
         project :

Possible solution:
 - Declare repository providing the artifact, see the documentation at https://docs.gradle.org/current/userguide/declaring_repositories.html

 

Pls, tell me how I can fix this error?

The version you are using is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.

Currently supported versions are 1.19.2 (Latest) and 1.18.2 (LTS).