java - Java递归读取文件夹中的所有文件

Question

我需要编写一个程序来读取文件夹路径stdin及其所有子文件夹，然后根据它们的扩展名打印出文件的数量。

它将被编译如下：

java Summary -r <path>

输出需要如下所示：

txt:
  number of files: 5
  combined size: 1202131
  largest file: 729224
  smallest file: 12323
pdf:
  number of files: 2
  etc...

有人可以帮我吗？我不知道如何处理它。

Answer 1

你可以从这样的东西开始递归地读取文件

public void listFilesForFolder(final File folder) {
    for (final File fileEntry : folder.listFiles()) {
        if (fileEntry.isDirectory()) {
            listFilesForFolder(fileEntry);
        } else {
            System.out.println(fileEntry.getName());
        }
    }
}

此代码由@rich 提供。

其余的细节是你必须解决的。

您可以查看阅读文件夹中的所有文件以获取更多详细信息

Answer 2

看看这个：列出java中目录和子目录中的文件，只包括部分文件路径

您将获得目录下所有文件的列表，然后您可以使用它 file.length()来获取大小。

Answer 3

与此代码类似的东西（来自http://www.javapractices.com/topic/TopicAction.do?Id=68）：

在 JDK 7 中：

import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.FileVisitor;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;

/** Recursive listing with SimpleFileVisitor in JDK 7. */
public final class FileListingVisitor {

  public static void main(String... aArgs) throws IOException{
    String ROOT = "C:\\test";
    FileVisitor<Path> fileProcessor = new ProcessFile();
    Files.walkFileTree(Paths.get(ROOT), fileProcessor);
  }

  private static final class ProcessFile extends SimpleFileVisitor<Path> {
    @Override public FileVisitResult visitFile(
      Path aFile, BasicFileAttributes aAttrs
    ) throws IOException {
      System.out.println("Processing file:" + aFile);
      return FileVisitResult.CONTINUE;
    }

    @Override  public FileVisitResult preVisitDirectory(
      Path aDir, BasicFileAttributes aAttrs
    ) throws IOException {
      System.out.println("Processing directory:" + aDir);
      return FileVisitResult.CONTINUE;
    }
  }
} 

在较旧的：

import java.util.*;
import java.io.*;

/**
* Recursive file listing under a specified directory.
*  
* @author javapractices.com
* @author Alex Wong
* @author anonymous user
*/
public final class FileListing {

  /**
  * Demonstrate use.
  * 
  * @param aArgs - <tt>aArgs[0]</tt> is the full name of an existing 
  * directory that can be read.
  */
  public static void main(String... aArgs) throws FileNotFoundException {
    File startingDirectory= new File(aArgs[0]);
    List<File> files = FileListing.getFileListing(startingDirectory);

    //print out all file names, in the the order of File.compareTo()
    for(File file : files ){
      System.out.println(file);
    }
  }

  /**
  * Recursively walk a directory tree and return a List of all
  * Files found; the List is sorted using File.compareTo().
  *
  * @param aStartingDir is a valid directory, which can be read.
  */
  static public List<File> getFileListing(
    File aStartingDir
  ) throws FileNotFoundException {
    validateDirectory(aStartingDir);
    List<File> result = getFileListingNoSort(aStartingDir);
    Collections.sort(result);
    return result;
  }

  // PRIVATE //
  static private List<File> getFileListingNoSort(
    File aStartingDir
  ) throws FileNotFoundException {
    List<File> result = new ArrayList<File>();
    File[] filesAndDirs = aStartingDir.listFiles();
    List<File> filesDirs = Arrays.asList(filesAndDirs);
    for(File file : filesDirs) {
      result.add(file); //always add, even if directory
      if ( ! file.isFile() ) {
        //must be a directory
        //recursive call!
        List<File> deeperList = getFileListingNoSort(file);
        result.addAll(deeperList);
      }
    }
    return result;
  }

  /**
  * Directory is valid if it exists, does not represent a file, and can be read.
  */
  static private void validateDirectory (
    File aDirectory
  ) throws FileNotFoundException {
    if (aDirectory == null) {
      throw new IllegalArgumentException("Directory should not be null.");
    }
    if (!aDirectory.exists()) {
      throw new FileNotFoundException("Directory does not exist: " + aDirectory);
    }
    if (!aDirectory.isDirectory()) {
      throw new IllegalArgumentException("Is not a directory: " + aDirectory);
    }
    if (!aDirectory.canRead()) {
      throw new IllegalArgumentException("Directory cannot be read: " + aDirectory);
    }
  }
} 

Answer 4

请使用以下代码。

public static void listFiles(final File folder) {
    for (final File fileEntry : folder.listFiles()) {
        if (fileEntry.isFile() && fileEntry.getName().endsWith(".txt")) {
            System.out.println(fileEntry.getName());
        }
    if (fileEntry.isFile() && fileEntry.getName().endsWith(".pdf")) {
            System.out.println(fileEntry.getName());
        }
     else {
            listFiles(fileEntry);
        }
    }
}

public static void main(String startingPath){
    File folder = new File(startingPath);
    listFiles(folder);
}