-NOTE- THIS IS FOR VERSION 1.8

I've been having trouble updating to 1.8. When I click play it goes back to the launcher and says this

java.lang.OutOfMemoryError: Java heap space
at java.awt.imageDataBufferInt.<init>(DataBufferInt.java:41)
at java.awt.image.Raster.createPackedraster(Raster.java:455)
at java.awt.image.DirectColorModel.createCompatibleWritableRaster(DirectColorModel.java:1015)
at java.awt.image.BufferedImage.<init>(BufferedImage.java:326)
at cuj.a(SourceFile:407)
at cua.b(SourceFile:238)
at cua.a(SourceFile:77)
at cxh.j(SourceFile:553)
at cxk.a(SourceFile:139)
at cvt.a(SourceFile:99)
at bsu.aj(SourceFile:473)
at bsu.a(SourceFile:299)
at net.minecraft.client.main.Main.main(SourceFile:120)

I have no idea what this means, I've looked it up on the internet and it looks like no one has the similar problem.