我不确定这是怎么回事，但我正在运行的程序给了我一个奇怪的错误。我在每个循环上得到一个ArrayIndexOutOfBoundsException：-1。整个错误如下：
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1
at com.thoughtworks.xstream.core.util.OrderRetainingMap.entrySet(OrderRetainingMap.java:77)
at java.util.HashMap.putMapEntries(HashMap.java:511)
at java.util.HashMap.putAll(HashMap.java:784)
at com.thoughtworks.xstream.core.util.OrderRetainingMap.<init>(OrderRetainingMap.java:36)
at com.thoughtworks.xstream.converters.reflection.FieldDictionary.buildMap(FieldDictionary.java:135)
at com.thoughtworks.xstream.converters.reflection.FieldDictionary.fieldsFor(FieldDictionary.java:76)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.visitSerializableFields(PureJavaReflectionProvider.java:126)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doMarshal(AbstractReflectionConverter.java:81)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.marshal(AbstractReflectionConverter.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:69)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:43)
at com.thoughtworks.xstream.core.TreeMarshaller.start(TreeMarshaller.java:82)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.marshal(AbstractTreeMarshallingStrategy.java:37)
at com.thoughtworks.xstream.XStream.marshal(XStream.java:895)
at com.thoughtworks.xstream.XStream.marshal(XStream.java:884)
at com.thoughtworks.xstream.XStream.toXML(XStream.java:857)
at com.thoughtworks.xstream.XStream.toXML(XStream.java:844)
at unl.cse.assignments.DataConverter.output(DataConverter.java:210)
at unl.cse.assignments.DataConverter.main(DataConverter.java:121)
第210行是pw.print行：
for(Product p : products)
{
if(AwardTicket.class.isInstance(p)){
xstream.alias("awardTicket", AwardTicket.class);
pw.print(xstream.toXML(p) + "\n");
}
}
（第121行只调用输出）
我一直在调查这个错误很长一段时间，我无法弄清楚它的原因。我认为xstream有问题，但我尝试了其他输出。