这是我的简单代码:
try
{
Element performances = new Element("performances");
Document doc = new Document(performances);
doc.setRootElement(performances);
performances.setAttribute(new Attribute("date", dateFormat.format(cal.getTime())));
Element uptime = new Element("uptime");
uptime.addContent(new Element("days").setText(new Long(duptime).toString()));
uptime.addContent(new Element("hours").setText(new Long(huptime).toString()));
uptime.addContent(new Element("minutes").setText(new Long(muptime).toString()));
uptime.addContent(new Element("seconds").setText(new Long(suptime).toString()));
doc.getRootElement().addContent(uptime);
XMLOutputter xmlOutput = new XMLOutputter();
xmlOutput.setFormat(Format.getPrettyFormat());
xmlOutput.output(doc, new FileWriter("/homa/mazzy/Scrivania/perfor_"+dateFormat.format(cal.getTime())+"xml"));
我得到了这个例外
Exception in thread "AWT-EventQueue-0" org.jdom2.IllegalAddException: The element "performances" could not be added as the root of the document: The Content already has an existing parent document
但我不知道这是什么意思。错误在哪里?