Access Transformers versus the more capable (in most ways) Mixin probably in a more complicated way than necessary

at\example_at.cfg

#Example AccessTransformer
public main.MainClass field_1000_a # number
public main.MainClass func_1000_a # addToNumber

at\MyClass.java

package at;

import main.MainClass;

// This is a class that uses Access Transformers to access otherwise inaccessible fields/methods.
public class MyClass {
    public static void main(String[] args) {
        MainClass thing = new MainClass;
        System.out.println(thing.addToNumber(thing.number)); //84   These lines use things declared public in
        thing.number = -1;                                   //     the AccessTransformer configuration.
        thing.printNumber(); // -1
    }
}

main\MainClass.java

package main;

// Fake obfuscated names are comments
public class MainClass {
    private int number = 42; // field_1000_a
    protected int addToNumber(int whatToAdd) { // func_1000_a
        return number + whatToAdd;
    }
    public void printNumber() { // func_1001_a
                                // Java accepts methods with the same name as long as the parameter counts
                                // are different. Forge sticks the obfuscated (notch) name at the end of the
                                // intermediary (searge) name, but gives a unique numerical ID to them all.
        System.out.println(number);
    }
}

mixin\MainClassMixin.java

package mixin;

import main.MainClass;
import org.spongepowered.asm.mixin.Mixin;
import org.spongepowered.asm.mixin.Shadow;
import org.spongepowered.asm.mixin.gen.Accessor;
import org.spongepowered.asm.mixin.gen.Invoker;

@Mixin(MainClass.class)
public abstract class MainClassMixin implements MainInterface {
    @Shadow private int number;
    
    public void setNumber(int number) {
        this.number = number;
    }
    
    @Accessor("number")
    public abstract int getNumber();
    
    @Invoker("addToNumber")
    public abstract int addNumbers();
}

mixin\MainInterface.java

package mixin;

// Interface to cast to in order to access things
public interface MainInterface {
    void setNumber(int number);
    int getNumber();
    int addNumbers(int number);
}

mixin\MyClass.java

package mixin;

import main.MainClass;

public class MyClass {
    public static void main(String[] args) {
        MainClass thing = new MainClass;
        System.out.println(((MainInterface) thing).addNumbers(((MainInterface) thing).getNumber)); // 84
        ((MainInterface) thing).setNumber(-1);
        thing.printNumber(); // -1
    }
}