Minecraft Forums

This error is almost certainly a Java error and not a minecraft error.
My suggestions would be uninstalling/reinstalling Java. As someone said 7 has been buggy so sticking with 6 could be better.
Restarting the computer
Checking you have the right version of Java. Issues crop up between having a 64-bit OS and a 32-bit Java. I get both to save problems.
Restoring the computer back to a point where it worked.

Quote from superllamah

SORRY FOR THE NECRO

Whenever I run the following code,

java -Xmx1024m -Xms1024m -jar "C:\Users\***\AppData\Roaming\.minecraft\bin\minecraft.jar"

I get this error.

Exception in thread "main" java.lang.NoClassDefFoundError: fx
	 at java.lang.Class.getDeclaredMethods0(Native Method)
	 at java.lang.Class.privateGetDeclaredMethods(Class.java:2442)
	 at java.lang.Class.getMethod0(Class.java:2685)
	 at java.lang.Class.getMethod(Class.java:1620)
	 at sun.launcher.LauncherHelper.getMainMethod(LauncherHelper.java:494)
	 at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:486)
Caused by: java.lang.ClassNotFoundException: fx
	 at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
	 at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
	 at java.security.AccessController.doPrivileged(Native Method)
	 at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
	 at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
	 at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
	 at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
	 ... 6 more

Any Ideas on what to do? the only reason i am posting here is because this thread has gotten good feedback.

Anything appreciated!

It looks as if the Java Virtual Machine can't find a class called main, which every java program has to have.
"Exception in thread "main" java.lang.NoClassDefFoundError: fx" Actually I should clarify in saying it can't find where it's declared exactly. That line is the key line that's contains the error that's throwing everything out.

As for solutions, I'm not sure but hopefully I've helped you to understand your problem.

*** Starting Minecraft ***
Minecraft version: 1.5.1
Minecraft.jar: minecraft.jar
WindowSize: 1280x720
Java path: C:\Program Files (x86)\Java\jre7\bin\java
Memory: 3072 MB
LauncherPath: /C:/Users/Jeff/Downloads/MagicLauncher_1.0.0.jar
Error occurred during initialization of VM
Could not reserve enough space for object heap
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

I have the SAME problem (like everybody else here) I (all seperately) reinstalled java, installed java 6, deleten minecraft and redownload it, restarted computer,closed webpages, do the cmd code thing, and all those combined! Nothing works.
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-sdr908 or A Slice Of Combustible Toast

I got a new Windows 8 laptop in December. It has great ram and memory and everything. Minecraft was working great for it and all until the 1.5 update came out. it first gave me the error when i would force update it for 1.5 it said it couldn't update. and now it pops up this:

|---------------------------------------------------------------------------------------|
| Java Virtual Machine Launcher |
|---------------------------------------------------------------------------------------|
| |
| ( \/ ) Error: Could not create the Java Virtual Machine. |
| ( /\ ) Error: A fatal exception has occurred. Program will exit. |
| |
| |
| ___________ |
| | OK | |
| |-----------------| |
| |
|----------------------------------------------------------------------------------------|


(^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^)
(This looked way better when typing it. its supose to be the error pop up box)


and it doesn't even open up minecraft. It started when the 1.5 minecraft update came out. when 1.5 came out, that message popped up most of the time but if i either rebooted the computer or after many times trying to open up minecraft i would maybe get lucky and it open, but it still didn't update. i borrowed my friends .minecraft file and that's how i got 1.5 but the JVML error kept popping up. when 1.5.1 came out i cant get minecraft to open what so ever. iv tried uninstalling and re-installing minecraft many times. same thing every time. Iv tried using different launchers, i.e. Technic launcher - vanila, to do it and same problem. Iv even tried to launch tekkit or technic or even voltz and same problem. Iv tried to play it in the browser mode at minecraft.net and the cant update error pops up. iv tried uninstalling and re-installing java many many time. same problems. i don't know what to do. iv checked to see if there are any viruses and there are none at all.
This is not an upgraded windows 7 to windows 8 laptop. this laptop came with windows 8 from factory.
Anyone can help me please?

WARNING THIS IS A VERY URGENT ANNOUNCEMENT!!!
Java 7 is a virus! the virus alters your virus software if it doesnt know that it is a virus meaning if you haven't updated it. it was actually causing mine to not upgrade at all. after i got around it, it deleted it. i installed java 6. everything works perfectly now 100%. if u havnt updated java yet from 6 to 7 dont do it. Again Java 7 is a virus.

Quote from fergstaz

The only things I had done recently on my computer was download a game called slender, Also MCPatcher to patch a texture pack but when I patched it, thats whenj I opened my minecraft and got this error

You used MCPatcher? that must of caused your minecraft to explode go to MCPatcher and there should be a unpatch button it might start working after that I'm guessing it was working before MCPatcher screwed up minecraft not sure if that's the prob though

I'm having the same problem on a pc I'm fixing for someone. Minecraft has never been run on here, all I have done was download the .exe file. When I try to run it I get the error:

"Could not create java virtual machine"

I have updated to the newest version of java, I have uninstalled java and re installed java and even downgraded to 1.6.0_45 and I still get the same error.

Java debug gives no errors with 1.6 or 1.7.

I tried using MagicLauncher and I get this error:

java.lang.ClassNotFoundException: net.minecraft.client.Minecraft
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at magic.launcher.Launcher.main(Unknown Source)

This pc has Win XP and only has 1g Ram so not sure if that is the problem.

I have tried running it through the .bat file and it does the same thing.

Any help would be appreciated...

i have the same dam problem when i tried installing divine rpg

Quote from AshenEdict

So, I found a rather idiotic solution. I just tested it several times and it works for me, but I have NO idea why. Just close all of your webpages and everything should work fine.

I usually just shut my PC down when it wasn't working and then opened it first thing because hey, maybe it just hasn't hit the error yet? Retarded logic, I know, but it seemed to work. Then, some times, it wouldn't work and then 45 minutes later BOOM! good and working. I found no rhyme or reason to this until I closed my browser to restart and hit MC by accident and, lo and behold, it opened. Then I opened my Chrome again, tried to open another MC and got the error, closed it and MC worked like a dream.

NO clue why this works, just seems to. Give it a shot and see if it works for you.

P.S. - I just copied this and then closed my browser and it worked, opened it, pasted this message and was greeted with a virtual machine error.

Hope this helps /:

EDIT: ... and now it's working with my browser open as long as I keep the original one open... what?

that actually worked.. thanks!

none of this is working for me
any more suggestions

java version "1.7.0_21"
Java(TM) SE Runtime Environment (build 1.7.0_21-b11)
Java HotSpot(TM) Client VM (build 23.21-b01, mixed mode, sharing)

I get the same thing, please help!

If you are getting this then please follow these steps: "Could not create the java virtual machine"
[1] Replace your current version of Java with Java 6..
[2] Login to the FTB launcher
[3] Launch the modpack
[4] It should work!!!

Quote from wolflover234

Dont install the new one- Java 6 is the one you need. Java 7 is having bad problems, And it may or may not of caused this problem. I have this problem to. Un install java, Then re install java 6. *Make sure you install the one that goes to your computer, Meaning if you have 64 bit, Download 64 bit Java 6, If you have 32 bit then download java 32 bit 6* Im learning Java, But this sadly makes no sence to me. The message will change once you install java 6 to: "Could not create the java virtual machine". It's better *Im guessing, Due to the less errors.* But still wont let Minectraft run. Im not sure and I cant help you more then that >:C... Sorry. If I find an answer, I'll tell you C:<

Yeah thanks, Pro tip, go to configuration>java>Views and disable 7 and enable 6.

This error keeps on popping up when I've tried to open minecraft and its making me angry so I've reinstalled java 7 and everything someone plz help meeeee

can you place a java 6 link

Can some 1 help me i get an error saying Error: could not create java virtual machine.I have java 6.PLEASE HELP ME !!!

Thanks!!! This topic really helped me out :).

Hi Guys,

So i have this problem aswell.The first thing what i did was i deleted minecraft bin hoping it will solve this problem.But sadly no.Then i deleted all MC Patchers i had and still it doesn`t work.I have a java jre1.6.0.
I also tried to restart my computer and then start minecraft.It didn`t work.So please can someone reply me with
any solution that i didn`t try yet.And if you were wondering what programs i downloaded recently:

rzr Skyrim
Hearthfire
Dawnguard
Dragonborn

this happens to me to but i found a way to still play minecraft. you can use the magic launcher it still works.
But that is for me at least

what should i really do?

Quote from magic_masterman

this happens to me to but i found a way to still play minecraft. you can use the magic launcher it still works.
But that is for me at least

how bout tekkit