Problem with creating and checking files

Hello. I am making a Minecraft launcher and I have run into a problem. It can start MC fine. But that would only work for one user so I then tried to get it to read a text file to get the username. If it couldn't find the file it would create it. This didn't work. This is my code:

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class launcher {

	public static BufferedReader in;
	public static String name = "Player";
	final static String fileName = "name.txt";
	final static File parentDir = new File("%APPDATA%\\.minecraft");
	public static File file = new File(parentDir, fileName);
	public static String c = "java -Xmx1024m -cp \"%APPDATA%\\.minecraft\\bin\\minecraft.jar;%APPDATA%\\.minecraft\\bin\\lwjgl.jar;%APPDATA%\\.minecraft\\bin\\lwjgl_util.jar;%APPDATA%\\.minecraft\\bin\\jinput.jar\" -Djava.library.path=\"%APPDATA%\\.minecraft\\bin\\natives\" net.minecraft.client.Minecraft \"" + name + "\"";

	public static void main(String[] args) {
		checkUser();
	}

	private static void runMC() {
		try {
			Runtime.getRuntime().exec("cmd /c" + c);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	private static void checkUser() {
		try {
			in = new BufferedReader(new FileReader("%APPDATA%.minecraft/name.txt"));
			name = in.readLine();
			runMC();
		} catch (FileNotFoundException e1) {
			e1.printStackTrace();
			createFile();
		} catch (IOException e1) {
			e1.printStackTrace();
		}
	}
	
	public static void createFile(){
		parentDir.mkdir();
		try {
			file.createNewFile();
			System.out.println("Created");
			checkUser();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

If anybody could help, that would be great!
Thanks in advance,
Curly