我想把foldera里面的文本文件移到folderb。但是，文件夹本身移动了，而不是里面的文件。有人能告诉我如何更改下面的代码吗？

File source = new File("d:/files/folderA/");
 File target = new File("d:/files/folderB/");                           

 boolean success = source.renameTo(new File(target, source.getName()));

 if (!success) {
            // File was not successfully moved
   }