Exception ticking world entities

When I loaded up a world it crashed 😞
(I played in it before)

---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 19-5-13 13:46
Description: Exception ticking world entities

java.lang.OutOfMemoryError: Java heap space
	at java.util.jar.JarFile.getBytes(Unknown Source)
	at java.util.jar.JarFile.getManifestFromReference(Unknown Source)
	at java.util.jar.JarFile.getInputStream(Unknown Source)
	at sun.misc.URLClassPath$JarLoader$2.getInputStream(Unknown Source)
	at sun.misc.Resource.cachedInputStream(Unknown Source)
	at sun.misc.Resource.getByteBuffer(Unknown Source)
	at java.net.URLClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.access$100(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at aaq.h(SourceFile:1238)
	at jb.h(SourceFile:394)
	at net.minecraft.server.MinecraftServer.s(SourceFile:472)
	at net.minecraft.server.MinecraftServer.r(SourceFile:407)
	at bhc.r(SourceFile:125)
	at net.minecraft.server.MinecraftServer.run(SourceFile:341)
	at gr.run(SourceFile:584)


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

-- Head --
Stacktrace:
	at java.util.jar.JarFile.getBytes(Unknown Source)
	at java.util.jar.JarFile.getManifestFromReference(Unknown Source)
	at java.util.jar.JarFile.getInputStream(Unknown Source)
	at sun.misc.URLClassPath$JarLoader$2.getInputStream(Unknown Source)
	at sun.misc.Resource.cachedInputStream(Unknown Source)
	at sun.misc.Resource.getByteBuffer(Unknown Source)
	at java.net.URLClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.access$100(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at aaq.h(SourceFile:1238)
	at jb.h(SourceFile:394)

-- Affected level --
Details:
	Level name: 1.6 derp world!
	All players: 1 total; [je['kingpulsar'/914970, l='1.6 derp world!', x=-1196,25, y=51,20, z=-704,59]]
	Chunk stats: ServerChunkCache: 811 Drop: 0
	Level seed: -7584639419886086157
	Level generator: ID 01 - flat, ver 0. Features enabled: true
	Level generator options: 2;7,3x1,52x24;2;
	Level spawn location: World: (-1295,4,-829), Chunk: (at 1,0,3 in -81,-52; contains blocks -1296,0,-832 to -1281,255,-817), Region: (-3,-2; contains chunks -96,-64 to -65,-33, blocks -1536,0,-1024 to -1025,255,-513)
	Level time: 161101 game time, 86951 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 8496 (now: false), thunder time: 7781 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.s(SourceFile:472)
	at net.minecraft.server.MinecraftServer.r(SourceFile:407)
	at bhc.r(SourceFile:125)
	at net.minecraft.server.MinecraftServer.run(SourceFile:341)
	at gr.run(SourceFile:584)

-- System Details --
Details:
	Minecraft Version: 13w19a
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_05, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 107362424 bytes (102 MB) / 931790848 bytes (888 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 619 (34664 bytes; 0 MB) allocated, 556 (31136 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 16 (896 bytes; 0 MB) allocated, 16 (896 bytes; 0 MB) used
	Player Count: 1 / 8; [je['kingpulsar'/914970, l='1.6 derp world!', x=-1196,25, y=51,20, z=-704,59]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.