Add a java version detection and nag system for users on Java 7 or below.

Added detection of mods that rely on Java 8 and a graceful error screen.
The nag screen will be shown once a day. It can be disabled by editing the forge.cfg.
However it is HIGHLY recomended that user update to Java 8.

patches/minecraft/net/minecraft/client/gui/GuiMainMenu.java.patch

@@ -38,7 +38,16 @@
          if (p_146284_1_.field_146127_k == 11)
          {
              this.field_146297_k.func_71371_a("Demo_World", "Demo_World", DemoWorldServer.field_73071_a);
-@@ -512,7 +521,16 @@
+@@ -493,6 +502,8 @@
+             this.func_73729_b(j + 155, k + 0, 0, 45, 155, 44);
+         }
+ 
++        this.field_73975_c = net.minecraftforge.client.ForgeHooksClient.renderMainMenu(this, this.field_146289_q, this.field_146294_l, this.field_146295_m, this.field_73975_c);
++
+         GlStateManager.func_179094_E();
+         GlStateManager.func_179109_b((float)(this.field_146294_l / 2 + 90), 70.0F, 0.0F);
+         GlStateManager.func_179114_b(-20.0F, 0.0F, 0.0F, 1.0F);
+@@ -512,7 +523,15 @@
              s = s + ("release".equalsIgnoreCase(this.field_146297_k.func_184123_d()) ? "" : "/" + this.field_146297_k.func_184123_d());
          }
  
@@ -52,11 +61,10 @@
 +                this.func_73731_b(this.field_146289_q, brd, 2, this.field_146295_m - ( 10 + brdline * (this.field_146289_q.field_78288_b + 1)), 16777215);
 +            }
 +        }
-+        net.minecraftforge.client.ForgeHooksClient.renderMainMenu(this, this.field_146289_q, this.field_146294_l, this.field_146295_m);
          String s1 = "Copyright Mojang AB. Do not distribute!";
          this.func_73731_b(this.field_146289_q, s1, this.field_146294_l - this.field_146289_q.func_78256_a(s1) - 2, this.field_146295_m - 10, -1);
  
-@@ -529,6 +547,7 @@
+@@ -529,6 +548,7 @@
          {
              this.field_183503_M.func_73863_a(p_73863_1_, p_73863_2_, p_73863_3_);
          }
@@ -64,3 +72,12 @@
      }
  
      protected void func_73864_a(int p_73864_1_, int p_73864_2_, int p_73864_3_) throws IOException
+@@ -549,6 +569,8 @@
+         {
+             this.field_183503_M.func_73864_a(p_73864_1_, p_73864_2_, p_73864_3_);
+         }
++
++        net.minecraftforge.client.ForgeHooksClient.mainMenuMouseClick(p_73864_1_, p_73864_2_, p_73864_3_, this.field_146289_q, this.field_146294_l);
+     }
+ 
+     public void func_146281_b()

src/main/java/net/minecraftforge/client/ForgeHooksClient.java

@@ -8,6 +8,7 @@ import static org.lwjgl.opengl.GL20.*;
 
 import java.nio.ByteBuffer;
 import java.nio.FloatBuffer;
+import java.util.Collections;
 import java.util.Map;
 
 import javax.vecmath.Matrix3f;
@@ -89,8 +90,12 @@ import net.minecraftforge.common.model.IModelPart;
 import net.minecraftforge.common.model.ITransformation;
 import net.minecraftforge.common.model.TRSRTransformation;
 import net.minecraftforge.fml.client.FMLClientHandler;
+import net.minecraftforge.fml.client.GuiJava8Error;
 import net.minecraftforge.fml.client.registry.ClientRegistry;
 import net.minecraftforge.fml.common.FMLLog;
+import net.minecraftforge.fml.common.Java8VersionException;
+import net.minecraftforge.fml.common.Loader;
+import net.minecraftforge.fml.common.ModContainer;
 
 import org.apache.commons.lang3.tuple.Pair;
 import org.lwjgl.BufferUtils;
@@ -266,7 +271,8 @@ public class ForgeHooksClient
         //RenderingRegistry.registerBlockHandler(RenderBlockFluid.instance);
     }
 
-    public static void renderMainMenu(GuiMainMenu gui, FontRenderer font, int width, int height)
+    private static int updatescrollcounter = 0;
+    public static String renderMainMenu(GuiMainMenu gui, FontRenderer font, int width, int height, String splashText)
     {
         Status status = ForgeVersion.getStatus();
         if (status == BETA || status == BETA_OUTDATED)
@@ -278,6 +284,17 @@ public class ForgeHooksClient
             gui.drawString(font, line, (width - font.getStringWidth(line)) / 2, 4 + (1 * (font.FONT_HEIGHT + 1)), -1);
         }
 
+        if (!Loader.instance().java8)
+        {
+            String line = I18n.format("fml.messages.java8warning.1", TextFormatting.RED, TextFormatting.RESET);
+            gui.drawString(font, line, (width - font.getStringWidth(line)) / 2, 4 + (8 * (font.FONT_HEIGHT + 1)), -1);
+            line = I18n.format("fml.messages.java8warning.2");
+            gui.drawString(font, line, (width - font.getStringWidth(line)) / 2, 4 + (9 * (font.FONT_HEIGHT + 1)), -1);
+            splashText = updatescrollcounter < 50 ? "UPDATE!" : "JAVA!";
+            updatescrollcounter+=1;
+            updatescrollcounter%=100;
+        }
+
         String line = null;
         switch(status)
         {
@@ -294,6 +311,24 @@ public class ForgeHooksClient
             // if we have a line, render it in the bottom right, above Mojang's copyright line
             gui.drawString(font, line, width - font.getStringWidth(line) - 2, height - (2 * (font.FONT_HEIGHT + 1)), -1);
         }
+
+        return splashText;
+    }
+
+    public static void mainMenuMouseClick(int mouseX, int mouseY, int mouseButton, FontRenderer font, int width)
+    {
+        if (!Loader.instance().java8)
+        {
+            if (mouseY >= (4 + (8 * 10)) && mouseY < (4 + (10 * 10)))
+            {
+                int w = font.getStringWidth(I18n.format("fml.messages.java8warning.1", TextFormatting.RED, TextFormatting.RESET));
+                w = Math.max(w, font.getStringWidth(I18n.format("fml.messages.java8warning.2")));
+                if (mouseX >= ((width - w) / 2) && mouseX <= ((width + w) / 2))
+                {
+                    FMLClientHandler.instance().showGuiScreen(new GuiJava8Error(new Java8VersionException(Collections.<ModContainer>emptyList())));
+                }
+            }
+        }
     }
 
     public static ISound playSound(SoundManager manager, ISound sound)

src/main/java/net/minecraftforge/common/ForgeModContainer.java

@@ -14,6 +14,7 @@ import java.net.URL;
 import java.security.cert.Certificate;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Date;
 import java.util.List;
 import java.util.Map;
 
@@ -74,6 +75,7 @@ public class ForgeModContainer extends DummyModContainer implements WorldAccessC
     public static boolean defaultHasSpawnFuzz = true;
     public static boolean forgeLightPipelineEnabled = true;
     public static boolean replaceVanillaBucketModel = true;
+    public static long java8Reminder = 0;
 
     private static Configuration config;
     private static ForgeModContainer INSTANCE;
@@ -259,6 +261,11 @@ public class ForgeModContainer extends DummyModContainer implements WorldAccessC
         replaceVanillaBucketModel = prop.getBoolean(Boolean.FALSE);
         propOrder.add(prop.getName());
 
+        prop = config.get(Configuration.CATEGORY_CLIENT, "java8Reminder", java8Reminder,
+                "The timestamp of the last reminder to update to Java 8 in number of milliseconds since January 1, 1970, 00:00:00 GMT. Nag will show only once every 24 hours. To disable it set this to some really high number.");
+        java8Reminder = prop.getLong(java8Reminder);
+        propOrder.add(prop.getName());
+
         config.setCategoryPropertyOrder(CATEGORY_CLIENT, propOrder);
 
         if (config.hasChanged())
@@ -267,6 +274,13 @@ public class ForgeModContainer extends DummyModContainer implements WorldAccessC
         }
     }
 
+    public static void updateNag()
+    {
+        Property prop = config.get(Configuration.CATEGORY_CLIENT, "java8Reminder", java8Reminder);
+        prop.set((new Date()).getTime());
+        config.save();
+    }
+
     /**
      * By subscribing to the OnConfigChangedEvent we are able to execute code when our config screens are closed.
      * This implementation uses the optional configID string to handle multiple Configurations using one event handler.

src/main/java/net/minecraftforge/common/config/Property.java

@@ -680,14 +680,7 @@ public class Property
      */
     public int getInt()
     {
-        try
+        return getInt(Integer.parseInt(defaultValue));
-        {
-            return Integer.parseInt(value);
-        }
-        catch (NumberFormatException e)
-        {
-            return Integer.parseInt(defaultValue);
-        }
     }
 
     /**
@@ -727,6 +720,54 @@ public class Property
         }
     }
 
+    /**
+     * Returns the value in this property as a long,
+     * if the value is not a valid long, it will return the initially provided default.
+     *
+     * @return The value
+     */
+    public long getLong()
+    {
+        return getLong(Long.parseLong(defaultValue));
+    }
+
+    /**
+     * Returns the value in this property as a long,
+     * if the value is not a valid long, it will return the
+     * provided default.
+     *
+     * @param _default The default to provide if the current value is not a validlong
+     * @return The value
+     */
+    public long getLong(long _default)
+    {
+        try
+        {
+            return Long.parseLong(value);
+        }
+        catch (NumberFormatException e)
+        {
+            return _default;
+        }
+    }
+
+    /**
+     * Checks if the current value stored in this property can be converted to a long.
+     * @return True if the type of the Property is an Long
+     */
+    public boolean isLongValue()
+    {
+        try
+        {
+            Long.parseLong(value);
+            return true;
+        }
+        catch (NumberFormatException e)
+        {
+            return false;
+        }
+    }
+
     /**
      * Returns the value in this property as a boolean,
      * if the value is not a valid boolean, it will return the
@@ -1148,6 +1189,7 @@ public class Property
         this.setValues(values);
     }
     public void set(int     value){ set(Integer.toString(value)); }
+    public void set(long    value){ set(Long.toString(value));    }
     public void set(boolean value){ set(Boolean.toString(value)); }
     public void set(double  value){ set(Double.toString(value));  }
 }

src/main/java/net/minecraftforge/fml/client/FMLClientHandler.java

@@ -19,6 +19,7 @@ import java.lang.ref.WeakReference;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.Date;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -69,6 +70,7 @@ import net.minecraft.util.StringUtils;
 import net.minecraft.world.WorldSettings;
 import net.minecraft.world.storage.SaveFormatComparator;
 import net.minecraft.world.storage.SaveFormatOld;
+import net.minecraftforge.common.ForgeModContainer;
 import net.minecraftforge.fml.client.registry.RenderingRegistry;
 import net.minecraftforge.fml.common.DummyModContainer;
 import net.minecraftforge.fml.common.DuplicateModsFoundException;
@@ -76,6 +78,7 @@ import net.minecraftforge.fml.common.FMLCommonHandler;
 import net.minecraftforge.fml.common.FMLContainerHolder;
 import net.minecraftforge.fml.common.FMLLog;
 import net.minecraftforge.fml.common.IFMLSidedHandler;
+import net.minecraftforge.fml.common.Java8VersionException;
 import net.minecraftforge.fml.common.Loader;
 import net.minecraftforge.fml.common.LoaderException;
 import net.minecraftforge.fml.common.MetadataCollection;
@@ -158,6 +161,8 @@ public class FMLClientHandler implements IFMLSidedHandler
 
     private boolean loading = true;
 
+    private Java8VersionException j8onlymods;
+
     private WrongMinecraftVersionException wrongMC;
 
     private CustomModLoadingErrorDisplayException customError;
@@ -212,6 +217,10 @@ public class FMLClientHandler implements IFMLSidedHandler
         {
             dupesFound = dupes;
         }
+        catch (Java8VersionException j8mods)
+        {
+            j8onlymods = j8mods;
+        }
         catch (MissingModsException missing)
         {
             modsMissing = missing;
@@ -297,7 +306,7 @@ public class FMLClientHandler implements IFMLSidedHandler
      */
     public void finishMinecraftLoading()
     {
-        if (modsMissing != null || wrongMC != null || customError!=null || dupesFound!=null || modSorting!=null)
+        if (modsMissing != null || wrongMC != null || customError!=null || dupesFound!=null || modSorting!=null || j8onlymods!=null)
         {
             SplashProgress.finish();
             return;
@@ -344,6 +353,8 @@ public class FMLClientHandler implements IFMLSidedHandler
         }
         loading = false;
         client.gameSettings.loadOptions(); //Reload options to load any mod added keybindings.
+        Loader.instance().loadingComplete();
+        SplashProgress.finish();
     }
 
     public void extendModList()
@@ -383,6 +394,10 @@ public class FMLClientHandler implements IFMLSidedHandler
         {
             showGuiScreen(new GuiWrongMinecraft(wrongMC));
         }
+        else if (j8onlymods != null)
+        {
+            showGuiScreen(new GuiJava8Error(j8onlymods));
+        }
         else if (modsMissing != null)
         {
             showGuiScreen(new GuiModsMissing(modsMissing));
@@ -401,10 +416,16 @@ public class FMLClientHandler implements IFMLSidedHandler
         }
         else
         {
-            Loader.instance().loadingComplete();
+            logMissingTextureErrors();
-            SplashProgress.finish();
+            if (!Loader.instance().java8)
+            {
+                if ((new Date()).getTime() >= ForgeModContainer.java8Reminder + (1000 * 60 * 60 * 24))
+                {
+                    showGuiScreen(new GuiJava8Error(new Java8VersionException(Collections.<ModContainer>emptyList())));
+                    ForgeModContainer.updateNag();
+                }
+            }
         }
-        logMissingTextureErrors();
     }
     /**
      * Get the server instance

src/main/java/net/minecraftforge/fml/client/GuiJava8Error.java

@@ -0,0 +1,140 @@
+/*
+ * Forge Mod Loader
+ * Copyright (c) 2012-2013 cpw.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the GNU Lesser Public License v2.1
+ * which accompanies this distribution, and is available at
+ * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+ *
+ * Contributors:
+ *     cpw - implementation
+ */
+
+package net.minecraftforge.fml.client;
+
+import net.minecraft.client.gui.GuiButton;
+import net.minecraft.client.gui.GuiErrorScreen;
+import net.minecraft.client.resources.I18n;
+import net.minecraft.util.text.TextFormatting;
+import net.minecraftforge.fml.common.FMLCommonHandler;
+import net.minecraftforge.fml.common.FMLLog;
+import net.minecraftforge.fml.common.Java8VersionException;
+import net.minecraftforge.fml.common.Loader;
+import net.minecraftforge.fml.common.ModContainer;
+import org.apache.logging.log4j.Level;
+
+import com.google.common.collect.Lists;
+
+import java.awt.*;
+import java.io.IOException;
+import java.net.URI;
+import java.util.List;
+
+public class GuiJava8Error extends GuiErrorScreen
+{
+    private Java8VersionException java8VersionException;
+    public GuiJava8Error(Java8VersionException java8VersionException)
+    {
+        super(null,null);
+        this.java8VersionException = java8VersionException;
+    }
+
+    @Override
+    public void initGui()
+    {
+        this.buttonList.clear();
+        this.buttonList.add(new GuiButton(1, 50, this.height - 38, this.width/2 -55, 20, I18n.format("fml.button.visitjavadownloads")));
+        if (java8VersionException.getMods().isEmpty())
+        {
+            this.buttonList.add(new GuiButton(3, this.width / 2 + 5, this.height - 38, this.width / 2 - 55, 20, I18n.format("fml.button.continue")));
+        }
+        else
+        {
+            this.buttonList.add(new GuiButton(2, this.width / 2 + 5, this.height - 38, this.width / 2 - 55, 20, I18n.format("menu.quit")));
+        }
+    }
+
+    @Override
+    protected void actionPerformed(GuiButton button) throws IOException
+    {
+        if (button.id == 1)
+        {
+            try
+            {
+                Desktop.getDesktop().browse(new URI("http://www.oracle.com/technetwork/java/javase/downloads/index.html"));
+            }
+            catch (Exception e)
+            {
+                FMLLog.log(Level.ERROR, e, "Problem launching browser");
+            }
+        }
+        else if (button.id == 2)
+        {
+            FMLCommonHandler.instance().exitJava(1,true);
+        }
+        else if (button.id == 3)
+        {
+            FMLClientHandler.instance().showGuiScreen(null);
+        }
+    }
+
+    @Override
+    public void drawScreen(int mouseX, int mouseY, float partialTicks)
+    {
+        this.drawDefaultBackground();
+        int offset = 25;
+        if (!java8VersionException.getMods().isEmpty())
+        {
+            this.drawCenteredString(this.fontRendererObj, I18n.format("fml.messages.java8problem", TextFormatting.RED, TextFormatting.BOLD, TextFormatting.RESET), this.width / 2, offset, 0xFFFFFF);
+        }
+        else
+        {
+            this.drawCenteredString(this.fontRendererObj, I18n.format("fml.messages.java8recommended", TextFormatting.RED, TextFormatting.BOLD, TextFormatting.RESET), this.width / 2, offset, 0xFFFFFF);
+        }
+        offset+=15;
+        this.drawCenteredString(this.fontRendererObj, I18n.format("fml.messages.javaversion", System.getProperty("java.version").split("\\.")[1], System.getProperty("java.version")), this.width / 2, offset, 0xFFFFFF);
+        offset += 10;
+        if (!java8VersionException.getMods().isEmpty())
+        {
+            this.drawCenteredString(this.fontRendererObj, I18n.format("fml.messages.upgradejavaorremove", TextFormatting.RED,TextFormatting.BOLD, TextFormatting.RESET), this.width / 2, offset, 0xFFFFFF);
+            offset += 15;
+            this.drawCenteredString(this.fontRendererObj, I18n.format("fml.messages.modslistedbelow", I18n.format("fml.messages.requirejava8")), this.width / 2, offset, 0xFFFFFF);
+            offset += 10;
+            this.drawCenteredString(this.fontRendererObj, I18n.format("fml.messages.countbadandgood", java8VersionException.getMods().size(), Loader.instance().getActiveModList().size()), this.width / 2, offset, 0xFFFFFF);
+            offset += 5;
+            for (ModContainer mc : java8VersionException.getMods())
+            {
+                offset += 10;
+                this.drawCenteredString(this.fontRendererObj, String.format("%s (%s)", mc.getName(), mc.getModId()), this.width / 2, offset, 0xEEEEEE);
+            }
+        }
+        else
+        {
+            String text = I18n.format("fml.messages.upgradejava", TextFormatting.RED,TextFormatting.BOLD, TextFormatting.RESET).replaceAll("\\\\n", "\n");
+            List<String> lines = Lists.newArrayList();
+            for (String line : text.split("\n"))
+            {
+                lines.addAll(this.fontRendererObj.listFormattedStringToWidth(line, this.width - this.fontRendererObj.FONT_HEIGHT * 4));
+            }
+
+            int maxWidth = 0;
+            for (String line : lines)
+            {
+                maxWidth = Math.max(maxWidth, this.fontRendererObj.getStringWidth(line));
+            }
+
+            for (String line : lines)
+            {
+                this.drawString(this.fontRendererObj, line, (this.width - maxWidth) / 2, offset, 0xFFFFFF);
+                offset += this.fontRendererObj.FONT_HEIGHT + 2;
+            }
+
+            offset += 15;
+        }
+        // super.super
+        for (int i = 0; i < this.buttonList.size(); ++i)
+        {
+            ((GuiButton)this.buttonList.get(i)).drawButton(this.mc, mouseX, mouseY);
+        }
+    }
+}

src/main/java/net/minecraftforge/fml/common/DummyModContainer.java

@@ -32,6 +32,7 @@ public class DummyModContainer implements ModContainer
     private ModMetadata md;
     private ArtifactVersion processedVersion;
     private String label;
+    private int classVersion;
 
     public DummyModContainer(ModMetadata md)
     {
@@ -213,4 +214,16 @@ public class DummyModContainer implements ModContainer
     {
         return null;
     }
+
+    @Override
+    public void setClassVersion(int classVersion)
+    {
+        this.classVersion = classVersion;
+    }
+
+    @Override
+    public int getClassVersion()
+    {
+        return this.classVersion;
+    }
 }

src/main/java/net/minecraftforge/fml/common/FMLModContainer.java

@@ -90,6 +90,7 @@ public class FMLModContainer implements ModContainer
     private Map<String, String> customModProperties;
     private ModCandidate candidate;
     private URL updateJSONUrl;
+    private int classVersion;
 
     public FMLModContainer(String className, ModCandidate container, Map<String, Object> modDescriptor)
     {
@@ -699,4 +700,16 @@ public class FMLModContainer implements ModContainer
     {
         return updateJSONUrl;
     }
+
+    @Override
+    public void setClassVersion(int classVersion)
+    {
+        this.classVersion = classVersion;
+    }
+
+    @Override
+    public int getClassVersion()
+    {
+        return this.classVersion;
+    }
 }

src/main/java/net/minecraftforge/fml/common/InjectedModContainer.java

@@ -214,4 +214,16 @@ public class InjectedModContainer implements ModContainer
     {
         return wrappedContainer.getUpdateUrl();
     }
+
+    @Override
+    public void setClassVersion(int classVersion)
+    {
+        wrappedContainer.setClassVersion(classVersion);
+    }
+
+    @Override
+    public int getClassVersion()
+    {
+        return wrappedContainer.getClassVersion();
+    }
 }

src/main/java/net/minecraftforge/fml/common/Java8VersionException.java

@@ -0,0 +1,43 @@
+/*
+ * Forge Mod Loader
+ * Copyright (c) 2012-2013 cpw.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the GNU Lesser Public License v2.1
+ * which accompanies this distribution, and is available at
+ * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+ *
+ * Contributors:
+ *     cpw - implementation
+ */
+
+package net.minecraftforge.fml.common;
+
+import java.util.List;
+
+public class Java8VersionException extends EnhancedRuntimeException
+{
+    private static final long serialVersionUID = 1L;
+    private final List<ModContainer> mods;
+
+    public Java8VersionException(List<ModContainer> mods)
+    {
+        super("Mods require Java 8");
+        this.mods = mods;
+    }
+
+    @Override
+    protected void printStackTrace(WrappedPrintStream stream)
+    {
+        stream.println("Mods requiring Java 8:");
+        for (ModContainer mc : mods)
+        {
+            stream.println(String.format("\t%s : %s", mc.getName(), mc.getModId()));
+        }
+        stream.println("");
+    }
+
+    public List<ModContainer> getMods()
+    {
+        return mods;
+    }
+}

src/main/java/net/minecraftforge/fml/common/Loader.java

@@ -161,6 +161,7 @@ public class Loader
     private File forcedModFile;
     private ModDiscoverer discoverer;
     private ProgressBar progressBar;
+    public final boolean java8;
 
     public static Loader instance()
     {
@@ -187,6 +188,14 @@ public class Loader
 
     private Loader()
     {
+        String[] ver = System.getProperty("java.version").split("\\.");
+        int major = Integer.parseInt(ver[1]);
+        java8 = major > 7;
+        if (!java8)
+        {
+            FMLLog.severe("The game is not running with Java 8. Forge recommends Java 8 for maximum compatibility with mods");
+        }
+
         modClassLoader = new ModClassLoader(getClass().getClassLoader());
         if (!mccversion.equals(MC_VERSION))
         {
@@ -489,6 +498,7 @@ public class Loader
         ModAPIManager.INSTANCE.manageAPI(modClassLoader, discoverer);
         disableRequestedMods();
         modController.distributeStateMessage(FMLLoadEvent.class);
+        checkJavaCompatibility();
         sortModList();
         ModAPIManager.INSTANCE.cleanupAPIContainers(modController.getActiveModList());
         ModAPIManager.INSTANCE.cleanupAPIContainers(mods);
@@ -543,6 +553,24 @@ public class Loader
         modController.transition(LoaderState.PREINITIALIZATION, false);
     }
 
+
+    private void checkJavaCompatibility()
+    {
+        if (java8) return;
+        List<ModContainer> j8mods = Lists.newArrayList();
+        for (ModContainer mc : getActiveModList())
+        {
+            if (mc.getClassVersion() >= 52)
+            {
+                j8mods.add(mc);
+            }
+        }
+        if (!j8mods.isEmpty())
+        {
+            throw new Java8VersionException(j8mods);
+        }
+    }
+
     public void preinitializeMods()
     {
         if (!modController.isInState(LoaderState.PREINITIALIZATION))

src/main/java/net/minecraftforge/fml/common/ModContainer.java

@@ -152,4 +152,8 @@ public interface ModContainer
     boolean shouldLoadInEnvironment();
 
     URL getUpdateUrl();
+
+    void setClassVersion(int classVersion);
+
+    int getClassVersion();
 }

src/main/java/net/minecraftforge/fml/common/discovery/ASMDataTable.java

@@ -35,6 +35,7 @@ public class ASMDataTable
         private String annotationName;
         private String className;
         private String objectName;
+        private int classVersion;
         private Map<String,Object> annotationInfo;
         public ASMData(ModCandidate candidate, String annotationName, String className, String objectName, Map<String,Object> info)
         {

src/main/java/net/minecraftforge/fml/common/discovery/JarDiscoverer.java

@@ -83,6 +83,7 @@ public class JarDiscoverer implements ITypeDiscoverer
                         table.addContainer(container);
                         foundMods.add(container);
                         container.bindMetadata(mc);
+                        container.setClassVersion(modParser.getClassVersion());
                     }
                 }
             }

src/main/resources/assets/forge/lang/en_US.lang

@@ -1,5 +1,5 @@
 commands.forge.usage=Use /forge <subcommand>. Subcommands are tps, track
-commands.forge.usage.tracking=Use /forge track <type> <duration>. Valid types are te (Tile Entities). Duration is < 60. 
+commands.forge.usage.tracking=Use /forge track <type> <duration>. Valid types are te (Tile Entities). Duration is < 60.
 commands.forge.tps.summary=%s : Mean tick time: %d ms. Mean TPS: %d
 
 commands.forge.tracking.te.enabled=Tile Entity tracking enabled for %d seconds.
@@ -153,4 +153,18 @@ fml.menu.mods.normal=Normal
 fml.menu.mods.search=Search:
 fml.menu.modoptions=Mod Options...
 
-item.forge.bucketFilled.name=%s Bucket
+item.forge.bucketFilled.name=%s Bucket
+
+fml.messages.java8problem=%s%sJava Update Required%s
+fml.messages.java8recommended=%s%sJava Update Recommended%s
+fml.messages.modslistedbelow=The mods listed below %s
+fml.messages.requirejava8=require Java 8
+fml.messages.java8warning.1=%sJAVA VERSION WARNING%s UPDATE JAVA!
+fml.messages.java8warning.2=You need to update Java
+fml.messages.javaversion=Your Java version is Java %s (version string %s)
+fml.messages.upgradejavaorremove=%s%sUpdate Java%s or remove these mods to play
+fml.messages.upgradejava=\n\nPros of updating to Java 8\n- Better Performance\n- Better Security\n- Better Compatibility with newer mods
+fml.messages.countbadandgood=%s of %s mods have this problem
+
+fml.button.visitjavadownloads=Oracle Java SE Downloads
+fml.button.continue=Continue