How to make FileFilter in java?

问题

like in title how to make filter to .txt files?

i wrote something like this but it has error :(

 private void jMenuItem1ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        JFileChooser chooser = new JFileChooser();
        int retval = chooser.showOpenDialog(null);

        String yourpath = "E:\\Programy Java\\Projekt_SR1\\src\\project_sr1";
        File directory = new File(yourpath);
        String[] myFiles;
        FilenameFilter filter = new FilenameFilter() {
        public boolean accept(File directory, String fileName) {
            return fileName.endsWith(".txt");
        }
        };
        myFiles = directory.list(filter);


        if(retval == JFileChooser.APPROVE_OPTION)
        {
            File myFile = chooser.getSelectedFile();
        }

回答1:

Here you will find some working examples. This is also a good example of FileFilter used in JFileChooser.

The basics are, you need to override FileFilter class and write your custom code in its accpet method. The accept method in above example is doing filtration based on file types:

public boolean accept(File file) {
    if (file.isDirectory()) {
      return true;
    } else {
      String path = file.getAbsolutePath().toLowerCase();
      for (int i = 0, n = extensions.length; i < n; i++) {
        String extension = extensions[i];
        if ((path.endsWith(extension) && (path.charAt(path.length() 
                  - extension.length() - 1)) == '.')) {
          return true;
        }
      }
    }
    return false;
}

Or more simpler to use is FileNameFilter which has accept method with filename as argument, so you don't need to get it manually.

回答2:

Try something like this...

String yourPath = "insert here your path..";
File directory = new File(yourPath);
String[] myFiles = directory.list(new FilenameFilter() {
    public boolean accept(File directory, String fileName) {
        return fileName.endsWith(".txt");
    }
});

回答3:

From JDK8 on words it is as simple as

final String extension = ".java";
final File currentDir = new File(YOUR_DIRECTORY_PATH);
File[] files = currentDir.listFiles((File pathname) -> pathname.getName().endsWith(extension));

回答4:

Since Java7 you can simply use FileNameExtensionFilter(String description, String... extensions)

A simple JFileChooser analog to the example would be:

JFileChooser fileChooser = new JFileChooser();
fileChooser.setFileFilter(new FileNameExtensionFilter("Text files", "txt"));

I know the question was answered long ago, but this is actually the simplest solution.

回答5:

Here is a little utility class that I created:

import java.io.File;
import java.io.FilenameFilter;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

/**
 * Convenience utility to create a FilenameFilter, based on a list of extensions
 */
public class FileExtensionFilter implements FilenameFilter {
    private Set<String> exts = new HashSet<String>();

    /**
     * @param extensions
     *            a list of allowed extensions, without the dot, e.g.
     *            <code>"xml","html","rss"</code>
     */
    public FileExtensionFilter(String... extensions) {
        for (String ext : extensions) {
            exts.add("." + ext.toLowerCase().trim());
        }
    }

    public boolean accept(File dir, String name) {
        final Iterator<String> extList = exts.iterator();
        while (extList.hasNext()) {
            if (name.toLowerCase().endsWith(extList.next())) {
                return true;
            }
        }
        return false;
    }
}

Usage:

       String[] files = new File("myfile").list(new FileExtensionFilter("pdf", "zip"));

回答6:

Another simple example:

public static void listFilesInDirectory(String pathString) {
  // A local class (a class defined inside a block, here a method).
  class MyFilter implements FileFilter {
    @Override
    public boolean accept(File file) {
      return !file.isHidden() && file.getName().endsWith(".txt");
    }
  }

  File directory = new File(pathString);
  File[] files = directory.listFiles(new MyFilter());

  for (File fileLoop : files) {
    System.out.println(fileLoop.getName());
  }
}

// Call it
listFilesInDirectory("C:\\Users\\John\\Documents\\zTemp");

// Output
Cool.txt
RedditKinsey.txt
...

回答7:

You are going wrong here:

int retval = chooser.showOpenDialog(null); 
public boolean accept(File directory, String fileName) {`
return fileName.endsWith(".txt");`
}

You first show the file chooser dialog and then apply the filter! This wont work. First apply the filter and then show the dialog:

public boolean accept(File directory, String fileName) {
        return fileName.endsWith(".txt");
}
int retval = chooser.showOpenDialog(null);

回答8:

File f = null;
File[] paths;

try {

    f = new File(dir);

    // filefilter
    FilenameFilter fileNameFilter = new FilenameFilter() {

        public boolean accept(File dir, String name) {

            if (name.lastIndexOf('.') > 0) {

                int lastIndex = name.lastIndexOf('.');
                String str = name.substring(lastIndex);

                if (str.equals("." + selectlogtype)) {
                    return true;
                }
            }
            return false;
        }
    };

    paths = f.listFiles(fileNameFilter);

    for (int i = 0; i < paths.length; i++) {
        try {

            FileWriter fileWriter = new FileWriter("C:/Users/maya02/workspace/ftp_log/filefilterlogtxt");
            PrintWriter bWriter = new PrintWriter(fileWriter);

            for (File writerpath1 : paths) {
                bWriter.println(writerpath1);
            }

            bWriter.close();
        } 
        catch (IOException e) { System.out.println("HATA!!"); }
    }
    System.out.println("path dosyaya aktarıldı!.");
} 
catch (Exception e) { }

回答9:

... What about using Apache's FileFilters from: org.apache.commons.io?

just like:

 import org.apache.commons.io.filefilter.FileFileFilter;
 import org.apache.commons.io.filefilter.WildcardFileFilter;

 ...

 File dir = new File(".");

 String[] filters = { "*.txt"};
 IOFileFilter wildCardFilter = new WildcardFileFilter(filters, IOCase.INSENSITIVE);

 String[] files = dir.list( wildCardFilter );
 for ( int i = 0; i < files.length; i++ ) {
     System.out.println(files[i]);
 }

来源：https://stackoverflow.com/questions/5603966/how-to-make-filefilter-in-java