当我运行这段代码时，文件被创建，但它是空的，尽管输出看起来还可以

import java.io.IOException;

public class JasonTest {
    public static void main(String[] args) throws IOException {
        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        TestJson tj = new TestJson(13, "kuku");
        gson.toJson(tj, new FileWriter("test.json"));
        System.out.println(gson.toJson(tj));

    }
}

输出：

{
  "num": 13,
  "text": "kuku"
}

Process finished with exit code 0