Ошибка в компиляции

Решил сделать проверку md5 в minecraft 1.4.2 взяв за основу тутор Сашка. Код вставил, подправил, осталась единственная проблема, при компиляции выдает это:

Код:

== MCP 7.19 (data: 7.19, client: 1.4.2, server: 1.4.2) ==
# found ff, ff patches, srgs, name csvs, doc csvs, param csvs, renumber csv, ast
yle, astyle config
== Recompiling client ==
> Cleaning bin
> Recompiling
'"C:\Program Files\Java\jdk1.7.0_02\bin\javac" -Xlint:-options -deprecation -g -
source 1.6 -target 1....' failed : 1
 
== ERRORS FOUND ==
 
src\minecraft\net\minecraft\src\GuiMainMenu.java:49: error: cannot find symbol
            HttpURLConnection httpurlconnection = (HttpURLConnection)(new URL("h
ttp://minecraft.uogames.ru/mcraftServer/MinecraftDownload/check.php?md5=" + calc
)).openConnection();
 
                                                                            ^
 
  symbol:  variable calc
  location: class GuiMainMenu
1 error
==================
 
!! Can not find server sources, try decompiling !!
Для продолжения нажмите любую клавишу . . .

Отрывок из GUIMainMenu.java:

Код:

package net.minecraft.src;
 
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.Random;
import net.minecraft.client.Minecraft;
import org.lwjgl.opengl.GL11;
import org.lwjgl.util.glu.GLU;
 
public class GuiMainMenu extends GuiScreen
{
    /** The RNG used by the Main Menu Screen. */
    private static final Random rand = new Random();
 
    /** Counts the number of screen updates. */
    private float updateCounter = 0.0F;
 
    /** The splash message. */
    private String splashText = "missingno";
    private GuiButton buttonResetDemo;
 
    /** Timer used to rotate the panorama, increases every tick. */
    private int panoramaTimer = 0;
 
    /**
    * Texture allocated for the current viewport of the main menu's panorama background.
    */
    private int viewportTexture;
 
    /** An array of all the paths to the panorama pictures. */
    private static final String[] titlePanoramaPaths = new String[] {"/title/bg/panorama0.png", "/title/bg/panorama1.png", "/title/bg/panorama2.png", "/title/bg/panorama3.png", "/title/bg/panorama4.png", "/title/bg/panorama5.png"};
 
    public boolean checkMd5(String s)
    {
        try
        {
            s = URLEncoder.encode(s, "UTF-8");
            HttpURLConnection.setFollowRedirects(false);
            HttpURLConnection httpurlconnection = (HttpURLConnection)(new URL("http://minecraft.uogames.ru/mcraftServer/MinecraftDownload/check.php?md5=" + calc)).openConnection();
            httpurlconnection.setRequestMethod("POST");
            httpurlconnection.setDoInput(true);
            httpurlconnection.setDoOutput(true);
            httpurlconnection.setUseCaches(false);
            httpurlconnection.setAllowUserInteraction(false);
            httpurlconnection.setInstanceFollowRedirects(false);
            httpurlconnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            BufferedReader bufferedreader = new BufferedReader(new InputStreamReader(httpurlconnection.getInputStream()));
            String s1 = bufferedreader.readLine();
            boolean flag = s1 != null && s1.equalsIgnoreCase("OK");
            bufferedreader.close();
            return flag;
        }
        catch(Exception exception)
        {
            return false;
        }
    }

Что не так?
P.S. Понимаю, вопрос нубский, но я абсолютно не знаю Java.

 

Он говорит что не понимает что такое переменная calc!

 

Спс