method does not override or implement a method from a supertype @Override

Ok, so, really simple question, I think. When I am creating a build using the gradlew build task, I will be told that various methods I am attempting to override don't exist. I was even told that it cannot find the basic symbol "Material.Rock" 

Quote

error: cannot find symbol
        super(Block.Properties.create(Material.ROCK)       );
                                              ^
  symbol:   variable ROCK
  location: class Material

Quote

import net.minecraft.block.material.Material;

The question is, when I run my build task, do I have to have the source code files for java in any particular directory?  The command says to import "net. minecraft. etcetera" and that line throws no errors, but somehow the build task cannot reference the ROCK material.

Similarly, the class in question implements "block" which implements "AbstractBlock" which absolutely has a "public BlockRenderType getRenderType" method, but the build task's error message tells me that there is no such method.

Here is the method that throws the error:

Quote

    @Override
    public BlockRenderType getRenderType(BlockState blockState) {
      return BlockRenderType.MODEL;
    }

Here is my version information

Quote

------------------------------------------------------------
Gradle 6.8.1
------------------------------------------------------------

Build time:   2021-01-22 13:20:08 UTC
Revision:     31f14a87d93945024ab7a78de84102a3400fa5b2

Kotlin:       1.4.20
Groovy:       2.5.12
Ant:          Apache Ant(TM) version 1.10.9 compiled on September 27 2020
JVM:          1.8.0_291 (Oracle Corporation 25.291-b10)
OS:           Windows 10 10.0 amd64

And I am using the forge veriosn found in "forge-1.16.5-36.1.0-mdk (1).zip"

So, Very simply, why can't gradel recognize any of the code I told it to import, and is that code supposed to be decompiled in some folder relative to my mod folder or is that unnecessary? I already have the code decompiled, so don't worry about that part.