Minecraft keeps crashing (Vanilla)

My minecraft keeps crashing whenever i log into a online server, i have no idea why but i do indeed have the crash report.

[20:36:48] [Client thread/INFO]: Setting user: APoisonPotato93
[20:36:48] [Client thread/INFO]: (Session ID is token:f32c25b375584675aa0b0b1eaed7fe4b:29ed969693cd41bda6666aa49813b952)
[20:36:53] [Client thread/INFO]: LWJGL Version: 2.9.4
[20:36:54] [Client thread/INFO]: Reloading ResourceManager: Default
[20:36:54] [Sound Library Loader/INFO]: Starting up SoundSystem...
[20:36:54] [Thread-6/INFO]: Initializing LWJGL OpenAL
[20:36:54] [Thread-6/INFO]: (The LWJGL binding of OpenAL. For more information, see )
[20:36:55] [Thread-6/INFO]: OpenAL initialized.
[20:36:55] [Sound Library Loader/INFO]: Sound engine started
[20:37:01] [Client thread/INFO]: Created: 512x512 textures-atlas
[20:37:09] [Client thread/INFO]: Connecting to mc.sparkade.net, 25565
[20:37:13] [Client thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.IndexOutOfBoundsException: readerIndex(1) + length(83) exceeds writerIndex(6): UnpooledHeapByteBuf(ridx: 1, widx: 6, cap: 6) at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_25] at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_25] at g.a(SourceFile:61) [1.8.4.jar:?] at ave.av(SourceFile:880) [1.8.4.jar:?] at ave.a(SourceFile:325) [1.8.4.jar:?] at net.minecraft.client.main.Main.main(SourceFile:124) [1.8.4.jar:?]
Caused by: java.lang.IndexOutOfBoundsException: readerIndex(1) + length(83) exceeds writerIndex(6): UnpooledHeapByteBuf(ridx: 1, widx: 6, cap: 6) at io.netty.buffer.AbstractByteBuf.checkReadableBytes(AbstractByteBuf.java:1175) ~[netty-all-4.0.23.Final.jar:4.0.23.Final] at io.netty.buffer.AbstractByteBuf.readBytes(AbstractByteBuf.java:655) ~[netty-all-4.0.23.Final.jar:4.0.23.Final] at em.readBytes(SourceFile:669) ~[1.8.4.jar:?] at em.c(SourceFile:243) ~[1.8.4.jar:?] at bcy.a(SourceFile:1291) ~[1.8.4.jar:?] at gg.a(SourceFile:52) ~[1.8.4.jar:?] at gg.a(SourceFile:9) ~[1.8.4.jar:?] at fh$1.run(SourceFile:13) ~[1.8.4.jar:?] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_25] at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_25] at g.a(SourceFile:60) ~[1.8.4.jar:?] ... 3 more
[20:37:13] [Client thread/INFO]: [CHAT] You have no new mail.

Now, if anyone could help me fix this, it would be much appreciated! Cheers.

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3 Answers

You should try reinstalling your Minecraft

Make sure you copy out the saves folder first, then remove the entire.minecraft folder.

2

As far as I see, it crashes when writing to a file(probably auto-saves). You either have an corrupted save directory or it's read-only or inaccessible or something like that.

I have just uninstalled Minecraft then re-installed it. It does indeed work now. I don't know why I didn't do this before i came on here and asked for help. Regardless, thank you for your help guys. :)

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