When i start and open my singleplayer map, it just says Server Closed and it closes down.

It worked for like 7h ago, but not now. i havent changed anything since that.

i have tried to restart my pc, reinstall minecraft and search on google about same problem but couldnt find anything.

---- Minecraft Crash Report ----
// I just don't know what went wrong

Time: 2015-10-10 20:56
Description: Exception ticking world

java.lang.OutOfMemoryError: Java heap space
at io.netty.buffer.UnpooledHeapByteBuf.<init>(UnpooledHeapByteBuf.java:45)
at io.netty.buffer.UnpooledByteBufAllocator.newHeapBuffer(UnpooledByteBufAllocator.java:43)
at io.netty.buffer.AbstractByteBufAllocator.heapBuffer(AbstractByteBufAllocator.java:136)
at io.netty.buffer.Unpooled.buffer(Unpooled.java:137)
at gp.a(SourceFile:36)
at gp.<init>(SourceFile:29)
at lt.b(SourceFile:107)
at lu.c(SourceFile:161)
at lo.d(SourceFile:207)
at net.minecraft.server.MinecraftServer.D(SourceFile:610)
at net.minecraft.server.MinecraftServer.C(SourceFile:546)
at bvw.C(SourceFile:154)
at net.minecraft.server.MinecraftServer.run(SourceFile:450)
at java.lang.Thread.run(Unknown Source)

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

– Head –
Stacktrace:
at io.netty.buffer.UnpooledHeapByteBuf.<init>(UnpooledHeapByteBuf.java:45)
at io.netty.buffer.UnpooledByteBufAllocator.newHeapBuffer(UnpooledByteBufAllocator.java:43)
at io.netty.buffer.AbstractByteBufAllocator.heapBuffer(AbstractByteBufAllocator.java:136)
at io.netty.buffer.Unpooled.buffer(Unpooled.java:137)
at gp.a(SourceFile:36)
at gp.<init>(SourceFile:29)
at lt.b(SourceFile:107)
at lu.c(SourceFile:161)
at lo.d(SourceFile:207)

– Affected level –
Details:
Level name: eh ja vene
All players: 1 total; [lq['LeDalahast'/273, l='eh ja vene', x=-191,32, y=57,00, z=220,61]]
Chunk stats: ServerChunkCache: 1089 Drop: 0
Level seed: 5514551461
Level generator: ID 04 - customized, ver 0. Features enabled: true
Level generator options:
Level spawn location: World: (-180,64,256), Chunk: (at 12,4,0 in -12,16; contains blocks -192,0,256 to -177,255,271), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Level time: 26130 game time, 26130 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 135496 (now: false), thunder time: 131278 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.D(SourceFile:610)
at net.minecraft.server.MinecraftServer.C(SourceFile:546)
at bvw.C(SourceFile:154)
at net.minecraft.server.MinecraftServer.run(SourceFile:450)
at java.lang.Thread.run(Unknown Source)

– System Details –
Details:
Minecraft Version: 15w41b
Operating System: Windows 8.1 (x86) version 6.3
Java Version: 1.8.0_45, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 15098744 bytes (14 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: 13, tallocated: 95
Profiler Position: N/A (disabled)
Player Count: 1 / 8; [lq['LeDalahast'/273, l='eh ja vene', x=-191,32, y=57,00, z=220,61]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.