Creating Flat World. (Tunnerles Dream)

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

Time: 8/23/15 12:15 AM
Description: Exception in server tick loop

java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOf(Arrays.java:3236)
at sun.misc.IOUtils.readFully(IOUtils.java:60)
at java.util.jar.JarFile.getBytes(JarFile.java:425)
at java.util.jar.JarFile.getManifestFromReference(JarFile.java:193)
at java.util.jar.JarFile.getInputStream(JarFile.java:461)
at sun.misc.URLClassPath$JarLoader$2.getInputStream(URLClassPath.java:776)
at sun.misc.Resource.cachedInputStream(Resource.java:77)
at sun.misc.Resource.getByteBuffer(Resource.java:160)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:442)
at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
at java.net.URLClassLoader$1.run(URLClassLoader.java:367)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:360)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at net.minecraft.server.MinecraftServer.D(SourceFile:627)
at net.minecraft.server.MinecraftServer.C(SourceFile:553)
at bux.C(SourceFile:152)
at net.minecraft.server.MinecraftServer.run(SourceFile:457)
at java.lang.Thread.run(Thread.java:745)

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

– System Details –
Details:
Minecraft Version: 15w34d
Operating System: Windows 10 (x86) version 10.0
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 919192 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; [lm['DanTMD'/644, l='Commandblock', x=-1612.50, y=237.00, z=50.50]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.