java.lang.OutOfMemoryError: Java heap space
   at java.io.ObjectOutputStream$HandleTable.growEntries(ObjectOutputStream.java:2344)
   at java.io.ObjectOutputStream$HandleTable.assign(ObjectOutputStream.java:2269)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1425)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
   at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
   at java.util.TreeMap.writeObject(TreeMap.java:2274)
   at sun.reflect.GeneratedMethodAccessor68.invoke(GeneratedMethodAccessor68.java:0)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:606)
   at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:988)
   at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1429)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
   at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1541)
   at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1506)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1429)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
   at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1375)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1171)
   at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
   at java.util.TreeMap.writeObject(TreeMap.java:2274)
   at sun.reflect.GeneratedMethodAccessor68.invoke(GeneratedMethodAccessor68.java:0)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:606)
   at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:988)
   at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1429)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)
   at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1541)
   at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1506)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1429)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1175)