Question

条件是，如果目录存在，则必须在该特定目录中创建文件而不创建新目录。

以下代码仅创建具有新目录但不适用于现有目录的文件。例如，目录名称就像＆＃34; GETDIRECTION＆＃34;

String PATH = "/remote/dir/server/";

String fileName = PATH.append(id).concat(getTimeStamp()).append(".txt");  

String directoryName = PATH.append(this.getClassName());   

File file  = new File(String.valueOf(fileName));

File directory = new File(String.valueOf(directoryName));

 if(!directory.exists()){

             directory.mkdir();
            if(!file.exists() && !checkEnoughDiskSpace()){
                file.getParentFile().mkdir();
                file.createNewFile();
            }
}
FileWriter fw = new FileWriter(file.getAbsoluteFile());
BufferedWriter bw = new BufferedWriter(fw);
bw.write(value);
bw.close();

Answer 1

此代码首先检查目录是否存在，否则创建目录，然后创建文件。请注意，我无法验证您的某些方法调用，因为我没有完整的代码，所以我假设调用getTimeStamp()和getClassName()之类的内容将工作。您还应该对使用任何IOException类时可能引发的java.io.*做一些事情 - 写入文件的函数应抛出此异常（并在其他地方处理），或者您应该直接在方法中做到这一点。另外，我假设id属于String类型 - 我不知道您的代码没有明确定义它。如果它是int之类的东西，你可能应该把它转换为String，然后像在这里一样在fileName中使用它。

此外，我根据我认为合适的情况，将append来电替换为concat或+。

public void writeFile(String value){
    String PATH = "/remote/dir/server/";
    String directoryName = PATH.concat(this.getClassName());
    String fileName = id + getTimeStamp() + ".txt";

    File directory = new File(directoryName);
    if (! directory.exists()){
        directory.mkdir();
        // If you require it to make the entire directory path including parents,
        // use directory.mkdirs(); here instead.
    }

    File file = new File(directoryName + "/" + fileName);
    try{
        FileWriter fw = new FileWriter(file.getAbsoluteFile());
        BufferedWriter bw = new BufferedWriter(fw);
        bw.write(value);
        bw.close();
    }
    catch (IOException e){
        e.printStackTrace();
        System.exit(-1);
    }
}

如果要在Microsoft Windows上运行代码，您可能不应该使用这样的裸路径名 - 我不确定它将如何处理文件名中的/。为了完全可移植性，您应该使用类似File.separator的内容来构建路径。

编辑：根据下面JosefScript的评论，没有必要测试目录是否存在。 directory.mkdir()调用如果创建了目录，则返回true，如果没有，则返回false，包括目录已存在的情况。

Answer 2

我建议Java8 +使用以下内容。

/**
 * Creates a File if the file does not exist, or returns a
 * reference to the File if it already exists.
 */
private File createOrRetrieve(final String target) throws IOException{

    final Path path = Paths.get(target);

    if(Files.notExists(path)){
        LOG.info("Target file \"" + target + "\" will be created.");
        return Files.createFile(Files.createDirectories(path)).toFile();
    }
    LOG.info("Target file \"" + target + "\" will be retrieved.");
    return path.toFile();
}

/**
 * Deletes the target if it exists then creates a new empty file.
 */
private File createOrReplaceFileAndDirectories(final String target) throws IOException{

    final Path path = Paths.get(target);
    // Create only if it does not exist already
    Files.walk(path)
        .filter(p -> Files.exists(p))
        .sorted(Comparator.reverseOrder())
        .peek(p -> LOG.info("Deleted existing file or directory \"" + p + "\"."))
        .forEach(p -> {
            try{
                Files.createFile(Files.createDirectories(p));
            }
            catch(IOException e){
                throw new IllegalStateException(e);
            }
        });

    LOG.info("Target file \"" + target + "\" will be created.");

    return Files.createFile(
        Files.createDirectories(path)
    ).toFile();
}

Answer 3

尽量使其尽可能简短。创建目录（如果该目录不存在），然后返回所需的文件：

/** Creates parent directories if necessary. Then returns file */
private static File fileWithDirectoryAssurance(String directory, String filename) {
    File dir = new File(directory);
    if (!dir.exists()) dir.mkdirs();
    return new File(directory + "/" + filename);
}

Answer 4

<强>码

// Create Directory if not exist then Copy a file.


public static void copyFile_Directory(String origin, String destDir, String destination) throws IOException {

    Path FROM = Paths.get(origin);
    Path TO = Paths.get(destination);
    File directory = new File(String.valueOf(destDir));

    if (!directory.exists()) {
        directory.mkdir();
    }
        //overwrite the destination file if it exists, and copy
        // the file attributes, including the rwx permissions
     CopyOption[] options = new CopyOption[]{
                StandardCopyOption.REPLACE_EXISTING,
                StandardCopyOption.COPY_ATTRIBUTES

        };
        Files.copy(FROM, TO, options);


}

Answer 5

使用java.nio.Path会很简单-

public static Path createFileWithDir(String directory, String filename) {
        File dir = new File(directory);
        if (!dir.exists()) dir.mkdirs();
        return Paths.get(directory + File.separatorChar + filename);
    }

Answer 6

如果创建基于Web的应用程序，更好的解决方案是检查目录是否存在，然后创建该文件（如果不存在）。如果存在，请重新创建。

    private File createFile(String path, String fileName) throws IOException {
       ClassLoader classLoader = getClass().getClassLoader();
       File file = new File(classLoader.getResource(".").getFile() + path + fileName);

       // Lets create the directory
       try {
          file.getParentFile().mkdir();
       } catch (Exception err){
           System.out.println("ERROR (Directory Create)" + err.getMessage());
       }

       // Lets create the file if we have credential
       try {
           file.createNewFile();
       } catch (Exception err){
           System.out.println("ERROR (File Create)" + err.getMessage());
       }
       return  file;
   }

Answer 7

java 8+版本

CLASS TC_B definition for testing.
   private:
      METHODS: M_B
         IMPORTING cut TYPE REF TO CL_A.

   METHOD M_B.
      cut->M_A().
   ENDMETHOD.

CLASS LCL_B definition deferred.
CLASS TC_B definition local friends LCL_B.
CLASS LCL_B definition final for testing.
   private:
      DATA: cut TYPE REF TO CL_A.
            env TYPE REF TO TC_B.

      METHODS: test_M_A for testing,
               setup.

   METHOD setup.
      CREATE OBJECTS cut, env.
   ENDMETHOD.

   METHOD test_M_A.
      env->M_B( cut ).
   ENDMETHOD.

Files.createDirectories

如果目录已经存在，则该方法不会引发异常。

如果目录不存在，则创建一个目录，然后在该目录中创建文件

7 个答案: