We play games

Experiencing some errors. going to see what the problem is an troubleshoot it.
error log here:

[SEVERE] Encountered an unexpected exception OutOfMemoryError
java.lang.OutOfMemoryError: Java heap space
at sun.reflect.GeneratedConstructorAccessor3.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at net.minecraft.server.v1_6_R3.WorldGenFactory.b(SourceFile:76)
at net.minecraft.server.v1_6_R3.StructureStart.a(SourceFile:86)
at net.minecraft.server.v1_6_R3.WorldGenFactory.a(SourceFile:64)
at net.minecraft.server.v1_6_R3.StructureGenerator.a(SourceFile:256)
at net.minecraft.server.v1_6_R3.StructureGenerator.a(SourceFile:25)
at net.minecraft.server.v1_6_R3.WorldGenBase.a(SourceFile:29)
at net.minecraft.server.v1_6_R3.ChunkProviderGenerate.recreateStructures(SourceFile:527)
at org.bukkit.craftbukkit.v1_6_R3.generator.NormalChunkGenerator.recreateStructures(NormalChunkGenerator.java:73)
at net.minecraft.server.v1_6_R3.ChunkProviderServer.loadChunk(ChunkProviderServer.java:181)
at net.minecraft.server.v1_6_R3.ChunkProviderServer.getChunkAt(ChunkProviderServer.java:105)
at net.minecraft.server.v1_6_R3.ChunkProviderServer.getChunkAt(ChunkProviderServer.java:84)
at net.minecraft.server.v1_6_R3.MinecraftServer.f(MinecraftServer.java:287)
at net.minecraft.server.v1_6_R3.MinecraftServer.a(MinecraftServer.java:252)
at net.minecraft.server.v1_6_R3.DedicatedServer.init(DedicatedServer.java:152)
at net.minecraft.server.v1_6_R3.MinecraftServer.run(MinecraftServer.java:393)
at net.minecraft.server.v1_6_R3.ThreadServerApplication.run(SourceFile:583)