Game won't start. goes to window saying JVM has run out of memory.

Put the summary of the bug you're having here---- Minecraft Crash Report ----
// I blame Dinnerbone.

Time: 6/15/14 5:32 PM
Description: Exception in server tick loop

java.lang.OutOfMemoryError: Java heap space

A detailed walkthrough of the error, its code path and all known details is as follows:
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– System Details –
Details:
Minecraft Version: 1.7.9
Operating System: Windows 7 (x86) version 6.1
Java Version: 1.7.0_55, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 445017368 bytes (424 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Player Count: 0 / 8; []
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

What actually happened was...:

Game won't start. goes to window saying JVM has run out of memory.

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...