getFolderName() 'possibly' not working

I may just be going about this all wrong, but I am trying to get a reference to the name of the world so that I can write a text file that loads with each world. I can get the coordinates.txt file to appear in the directory above the 'saves' folder, but I need it to be different for each world. Each new map I make loads the same coordinates file created from the last world. Here is the java file im using the code in.

package com.exline.dbzmod;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.file.Path;
import java.util.List;

import com.exline.dbzmod.block.ModWorldGen;
import com.exline.dbzmod.block.ModWorldGenAgain;

import net.minecraft.client.Minecraft;
import net.minecraft.server.MinecraftServer;
import net.minecraft.server.management.PlayerList;
import net.minecraft.world.World;
import net.minecraft.world.WorldSavedData;
import net.minecraft.world.WorldSavedDataCallableSave;
import net.minecraftforge.common.DimensionManager;
import net.minecraftforge.fml.common.FMLCommonHandler;
import net.minecraftforge.fml.common.ModClassLoader;
import net.minecraftforge.fml.common.registry.GameRegistry;
import net.minecraftforge.fml.server.FMLServerHandler;

//find nearest dragonball
//this just updates the radar coordinates when called
//called in DragonBallEventHandler when corresponding block is destroyed

public class FindNearest 
{
	public static int xto;
	public static int zto;
	
	public static void init() throws Exception
	{
		xto = ModWorldGen.x0;
		zto = ModWorldGen.z0;
		String dir;

		MinecraftServer mc = FMLCommonHandler.instance().getMinecraftServerInstance();
		if (mc != null)
		{
			dir = mc.getFolderName();
		}
		else
		{
			dir = null;
		}
		
		if (dir != null)
		{
			File varTmpDir = new File("/saves/"+dir+"/coordinates.txt");
			boolean exists = varTmpDir.exists();
		
			if(exists != true) 
			{
				saveCoordinates();
			}
			else
			{
				loadCoordinates();
			}
		}
	}
	
	public static void findOne() throws Exception
	{
		xto = ModWorldGen.x1;
		zto = ModWorldGen.z1;
		
		saveCoordinates();
	}
	
	public static void findTwo() throws Exception
	{
		xto = ModWorldGen.x2;
		zto = ModWorldGen.z2;
		
		saveCoordinates();
	}
	
	public static void findThree() throws Exception
	{
		xto = ModWorldGen.x3;
		zto = ModWorldGen.z3;
		
		saveCoordinates();
	}
	
	public static void findFour() throws Exception
	{
		xto = ModWorldGen.x4;
		zto = ModWorldGen.z4;
		
		saveCoordinates();
	}
	
	public static void findFive() throws Exception
	{
		xto = ModWorldGen.x5;
		zto = ModWorldGen.z5;
		
		saveCoordinates();
	}
	
	public static void findSix() throws Exception
	{
		xto = ModWorldGen.x6;
		zto = ModWorldGen.z6;
		
		saveCoordinates();
	}
	
	public static void findSeven() throws Exception
	{
		//this method resets the dragon balls positions and re-spawns them in the world
		
		ModWorldGen.x0 += 120;
		ModWorldGen.z0 += 120;
		
		ModWorldGen.x1 -= 120;
		ModWorldGen.z1 -= 120;
		
		ModWorldGen.x2 += 120;
		ModWorldGen.z2 -= 120;
		
		ModWorldGen.x3 -= 120;
		ModWorldGen.z3 += 120;
		
		ModWorldGen.x4 += 120;
		ModWorldGen.z4 -= 120;
		
		ModWorldGen.x5 -= 120;
		ModWorldGen.z5 += 120;
		
		ModWorldGen.x6 -= 300;
		ModWorldGen.z6 += 300;
		
		xto = ModWorldGen.x0;
		zto = ModWorldGen.z0;
		
		saveCoordinates();
		
		GameRegistry.registerWorldGenerator(new ModWorldGenAgain(), 1);
	}
	
	public static void saveCoordinates() throws Exception
	{
		String dir;
		
		MinecraftServer mc = FMLCommonHandler.instance().getMinecraftServerInstance();
		if (mc != null)
		{
			dir = mc.getFolderName();
		}
		else
		{
			dir = null;
		}
		
		if (dir != null)
		{
		
			FileWriter saveFile = new FileWriter("/saves/"+dir+"/coordinates.txt");
			//write data to file now!!!
			saveFile.write("\n");
			saveFile.write(xto + "\n");
			saveFile.write(zto + "\n");
			saveFile.write("\n");
			//close filewriter
			saveFile.close();
		}
	}
	public static void loadCoordinates() throws Exception
	{
		String dir;
		
		MinecraftServer mc = FMLCommonHandler.instance().getMinecraftServerInstance();
		if (mc != null)
		{
			dir = mc.getFolderName();
		}
		else
		{
			dir = null;
		}
		
		if (dir != null)
		{		
			BufferedReader saveFile = new BufferedReader(new FileReader("/saves/"+dir+"/coordinates.txt"));
			// Throw away the blank line at the top.
			saveFile.readLine(); 
			// Get the integer value from the String.
			xto = Integer.parseInt(saveFile.readLine()); 
			zto = Integer.parseInt(saveFile.readLine());
		    
			saveFile.close();
		}
	}
		
}