Java，无法在Windows上删除文件

Question

我的应用程序有一个简单的更新程序。在代码中，我正在下载一个新版本，删除旧版本并将新版本重命名为旧版本。

它在 Linux 上运行良好。但在 Windows 上不起作用。没有异常(exception)或其他情况。附: RemotePlayer.jar 是当前运行的应用程序。

更新:

不起作用 - 这意味着在 file.delete() 和 file.renameTo(...) 之后文件仍然存在。我使用 sun java 7。(因为我使用 JavaFX)。

附注对不起我的英语。

public void checkUpdate(){
    new Thread(new Runnable() {
        @Override
        public void run() {
            System.err.println("Start of checking for update.");
            StringBuilder url = new StringBuilder();
            url.append(NetworkManager.SERVER_URL).append("/torock/getlastversionsize");
            File curJarFile = null;
            File newJarFile  = null;

            try {
                curJarFile = new File(new File(".").getCanonicalPath() + "/Player/RemotePlayer.jar");
                newJarFile = new File(new File(".").getCanonicalPath() + "/Player/RemotePlayerTemp.jar");
                if (newJarFile.exists()){
                    newJarFile.delete();
                }
            } catch (IOException e) {
                e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
                System.err.println("Cannot find curr Jar file");
                return;
            }

            if (curJarFile.exists()){
                setAccesToFile(curJarFile);
                try {
                    String resp = NetworkManager.makeGetRequest(url.toString());
                    JSONObject jsresp = new JSONObject(resp);
                    if (jsresp.getString("st").equals("ok")){
                        if (jsresp.getInt("size") != curJarFile.length()){
                            System.out.println("New version available, downloading started.");
                            StringBuilder downloadURL = new StringBuilder();
                            downloadURL.append(NetworkManager.SERVER_URL).append("/torock/getlatestversion");

                            if (NetworkManager.downLoadFile(downloadURL.toString(), newJarFile)){

                                if (jsresp.getString("md5").equals(Tools.md5File(newJarFile))){
                                    setAccesToFile(newJarFile);
                                    System.err.println("Deleting old version. File = " + curJarFile.getCanonicalPath());

                                    boolean b = false;
                                    if (curJarFile.canWrite() && curJarFile.canRead()){
                                        curJarFile.delete();
                                    }else System.err.println("Cannot delete cur file, doesn't have permission");

                                    System.err.println("Installing new version. new File = " + newJarFile.getCanonicalPath());

                                    if (curJarFile.canWrite() && curJarFile.canRead()){
                                        newJarFile.renameTo(curJarFile);
                                        b = true;
                                    }else System.err.println("Cannot rename new file, doesn't have permission");

                                    System.err.println("last version has been installed. new File  = " + newJarFile.getCanonicalPath());

                                    if (b){
                                        Platform.runLater(new Runnable() {
                                            @Override
                                            public void run() {
                                                JOptionPane.showMessageDialog(null, String.format("Внимание, %s", "Установлена новая версия, перезапустите приложение" + "", "Внимание", JOptionPane.ERROR_MESSAGE));

                                            }
                                        });
                                    }
                                }else System.err.println("Downloading file failed, md5 doesn't match.");
                            }
                        } else System.err.println("You use latest version of application");
                    }
                }catch (Exception e){
                    e.printStackTrace();
                    System.err.println("Cannot check new version.");
                }

            }else {
                System.err.println("Current jar file not found");
            }
        }
    }).start();
}

private void setAccesToFile(File f){
    f.setReadable(true, false);
    f.setExecutable(true, false);
    f.setWritable(true, false);
}

Answer 1

我找到了这个问题的解决方案。删除问题发生在我的案例中，因为-:

File f1=new File("temp.txt");
RandomAccessFile raf=new RandomAccessFile(f1,"rw");
f1.delete();//The file will not get deleted because raf is open on the file to be deleted

但如果我在调用 delete 之前关闭 RandomAccessFile，那么我就可以删除该文件。

File f1=new File("temp.txt");
RandomAccessFile raf=new RandomAccessFile(f1,"rw");
raf.close();
f1.delete();//Now the file will  get deleted

因此我们必须在调用 delete weather 之前检查任何对象(如 FileInputStream、RandomAccessFile)是否在该文件上打开。如果是，那么我们必须在对该文件调用 delete 之前关闭该对象。