My Minecraft will not load

Minecraft will not load... The startup screen stays for ever and eventually comes back with below message

// Oh - I know what I did wrong!

Time: 7/9/13 8:35 PM
Description: Exception in server tick loop

java.lang.OutOfMemoryError: Java heap space
	at java.util.Arrays.copyOfRange(Unknown Source)
	at java.lang.String.<init>(Unknown Source)
	at java.lang.StringBuilder.toString(Unknown Source)
	at java.lang.StackTraceElement.toString(Unknown Source)
	at java.lang.String.valueOf(Unknown Source)
	at java.lang.StringBuilder.append(Unknown Source)
	at java.lang.Throwable.printStackTrace(Throwable.java:657)
	at java.lang.Throwable.printStackTrace(Throwable.java:642)
	at java.lang.Throwable.printStackTrace(Throwable.java:633)
	at java.lang.Thread.dumpStack(Unknown Source)
	at adq.a(SourceFile:505)
	at aed.a(SourceFile:283)
	at aed.a(SourceFile:73)
	at aed.a(SourceFile:61)
	at jq.f(SourceFile:127)
	at jq.c(SourceFile:78)
	at jp.<init>(SourceFile:29)
	at jo.a(SourceFile:208)
	at jo.a(SourceFile:240)
	at hm.a(SourceFile:141)
	at hm.c(SourceFile:188)
	at hm.a(SourceFile:85)
	at bkz.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:488)
	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
	at bkw.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
	at hh.run(SourceFile:582)


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

-- System Details --
Details:
	Minecraft Version: 1.6.2
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 447787000 bytes (427 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 1 total; -Xmx512M
	AABB Pool Size: 2010 (112560 bytes; 0 MB) allocated, 1910 (106960 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 245 (13720 bytes; 0 MB) allocated, 245 (13720 bytes; 0 MB) used
	Player Count: 1 / 8; [ju['myegel'/173, l='Poki city', x=439.00, y=114.00, z=-250.67]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.