这是许多应用程序的一个相对常见的问题，而不是只是JDOM。

This is a relatively common problem with many applications, not just JDOM.

当你创建一个FileOutputStream并写入它时，你 必须冲它并关闭它 退出程序之前。

When you create a FileOutputStream, and write to it, you HAVE TO FLUSH IT AND CLOSE IT before exiting your program.

更改：

xmlOutput.output(doc, new FileOutputStream(new File("./src/Lexicon.xml")));

（使用try-with-resources）：

to be (using try-with-resources):

try (OutputStream fileout = new FileOutputStream(new File("./src/Lexicon.xml"))) {
    xmlOutput.output(doc, fileout);
}

或：

OutputStream fileout = new FileOutputStream(new File("./src/Lexicon.xml"));
xmlOutput.output(doc, fileout);
fileout.flush();
fileout.close();