I wish to alter some value in this mod as my friends adivced, so I got source code on it and rewrite a version by myself. but I was so inexperienced. when my built JAR file added to my game and ran, it crashed.
Here's part of the crash report.
net.minecraftforge.fml.common.LoaderExceptionModCrash: Caught exception from CyberwareE (cyberware_enhance) Caused by: java.lang.NoSuchMethodError: net.minecraft.util.NonNullList.create()Lnet/minecraft/util/NonNullList; at flaxbeard.cyberware.common.CyberwareConfig.preInit(CyberwareConfig.java:93) at flaxbeard.cyberware.Cyberware.preInit(Cyberware.java:45) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:624) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91) at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150) at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76) at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399) at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71) at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116) at com.google.common.eventbus.EventBus.post(EventBus.java:217) at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:219) at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:197) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91) at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150) at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76) at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399) at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71) at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116) at com.google.common.eventbus.EventBus.post(EventBus.java:217) at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:136) at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:627) at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:252) at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:467) at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:378) at net.minecraft.client.main.Main.main(SourceFile:123) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
By the way, it run well when debuging (despite many warnings).
Anyone could help me, please?

Now I post warning message when building.
warnings like this:
`

Configure project :
This mapping 'stable_39' was designed for MC 1.12! Use at your own peril.
WARNING: You are using an unsupported version of ForgeGradle.
Please consider upgrading to ForgeGradle 5 and helping in the efforts to get old versions working on the modern toolchain.
See https://gist.github.com/TheCurle/fe7ad3ede188cbdd15c235cc75d52d4a for more info on contributing.
`
hope it will be helpful.

Lately, I found that all .class files build throught ForgeGradle have failed to turned MCP name inside them to SRG name, and it proved to be the source of prblems. But I have no idea how does it take place.