Single Player doesn't work

Everytime I try to run Singleplayer, my game crashes. Can somebody who can read/understand code help me? Here's the report.


---- Minecraft Crash Report ----
// Don't be sad, have a hug! <3

Time: 10/2/15 5:07 PM
Description: Exception generating new chunk

java.lang.OutOfMemoryError: Java heap space
at amw.<init>(SourceFile:9)
at amz.<init>(ExtendedBlockStorage.java:44)
at amy.<init>(SourceFile:103)
at anv.d(SourceFile:127)
at ld.c(SourceFile:87)
at lc$a.<init>(SourceFile:39)
at lc.a(SourceFile:231)
at lc.a(SourceFile:263)
at lx.a(SourceFile:225)
at lx.c(SourceFile:277)
at lx.a(SourceFile:132)
at lo.b(SourceFile:110)
at lo.c(SourceFile:56)
at ek.a(SourceFile:221)
at ll.c(SourceFile:168)
at net.minecraft.server.MinecraftServer.B(SourceFile:625)
at net.minecraft.server.MinecraftServer.A(SourceFile:535)
at bpo.A(IntegratedServer.java:252)
at net.minecraft.server.MinecraftServer.run(SourceFile:451)
at java.lang.Thread.run(Thread.java:745)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
at amw.<init>(SourceFile:9)
at amz.<init>(ExtendedBlockStorage.java:44)
at amy.<init>(SourceFile:103)
at anv.d(SourceFile:127)

-- Chunk to be generated --
Details:
Location: -59,-25
Position hash: -103079215163
Generator: FlatLevelSource
Stacktrace:
at ld.c(SourceFile:87)
at lc$a.<init>(SourceFile:39)
at lc.a(SourceFile:231)
at lc.a(SourceFile:263)
at lx.a(SourceFile:225)
at lx.c(SourceFile:277)
at lx.a(SourceFile:132)
at lo.b(SourceFile:110)
at lo.c(SourceFile:56)
at ek.a(SourceFile:221)

-- Ticking connection --
Details:
Connection: ek@1412fef
Stacktrace:
at ll.c(SourceFile:168)
at net.minecraft.server.MinecraftServer.B(SourceFile:625)
at net.minecraft.server.MinecraftServer.A(SourceFile:535)
at bpo.A(IntegratedServer.java:252)
at net.minecraft.server.MinecraftServer.run(SourceFile:451)
at java.lang.Thread.run(Thread.java:745)

-- System Details --
Details:
Minecraft Version: 1.8.4
Operating System: Windows Vista (x86) version 6.0
CPU: 2x AMD Athlon(tm) 64 X2 Dual Core Processor 5000+
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 2064 bytes (0 MB) / 523501568 bytes (499 MB) up to 523501568 bytes (499 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [lf['Mythheart1'/3, l='Tree Fort', x=-639.50, y=237.00, z=-501.50]]
Type: Integrated Server (map_client.txt)
Is Modded: Very likely; Jar signature invalidated