java.lang.OutOfMemoryError: Java heap space
   at java.io.ObjectOutputStream$HandleTable.growEntries(ObjectOutputStream.java:2347)
   at java.io.ObjectOutputStream$HandleTable.assign(ObjectOutputStream.java:2276)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1428)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
   at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
   at java.util.TreeMap.writeObject(TreeMap.java:2434)
   at sun.reflect.GeneratedMethodAccessor392.invoke(GeneratedMethodAccessor392.java:0)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:483)
   at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:988)
   at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
   at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
   at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
   at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1378)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
   at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
   at java.util.TreeMap.writeObject(TreeMap.java:2434)
   at sun.reflect.GeneratedMethodAccessor392.invoke(GeneratedMethodAccessor392.java:0)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:483)
   at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:988)
   at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
   at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
   at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)