how to list certain files in a given directory in java

hey all...
I am a newbie in java and looking for how to list .java files in a given directory ( it should also include subdirectories ) and number of lines in that java files also should be listed. like that:

in c:\temp

tempp.java 22 line
helloo.java 7 line

etc.

Code:

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// This is one way to do it:
File filbert = new File("C:\\temp");
File[] fileList = filber.listFiles();

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Quote:

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to list .java files in a given directory ( it should also include subdirectories ) and number of lines in that java files also should be listed

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Several parts to this.
1) Use a filter object with the File list method to chose which files you want listed.
2) To get subdirectories, you'll need a search method (often recursive ) to go into sub directorires
3) To get the number of lines in a file, you'll have to read the file and count the number of newline characters.

Now i m googleing how to use a filter object
thanks much for the hints..

The file filter is a simple class that implements an interface. The interface has a method that is given the filename and returns a boolean. Read the API doc for the particulars.

Code:

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import java.io.*;

public class TraversingFiles {
    static int totalFiles = 0;

    public static void main(String[] args) {
        String path = ".";  // current directory
        File file = new File(path);
        System.out.println("parent folder = " + file.getName());
        File[] files = file.listFiles(new TextFilter());
        traverse(files);
        System.out.println("totalFiles = " + totalFiles);
    }

    private static void traverse(File[] files) {
        for(int i = 0; i < files.length; i++) {
            if(files[i].isDirectory()) {
                System.out.println("____folder: " + files[i].getName() +
                                  "____");
                traverse(files[i].listFiles(new TextFilter()));
                continue;
            }
            int lines = getLines(files[i]);
            System.out.printf("%50s  %3d lines%n", files[i].getName(), lines);
            totalFiles++;
        }
    }

    private static int getLines(File file) {
        int count = 0;
        try {
            BufferedReader br = new BufferedReader(
                                new InputStreamReader(
                                new FileInputStream(file)));
            while(br.readLine() != null) {
                count++;
            }
            br.close();
        } catch(IOException e) {
            System.out.println("read error for " + file.getPath() +
                              ": " + e.getMessage());
        }
        return count;
    }
}

class TextFilter implements FileFilter {
    String JAVA = "java";
    String TXT  = "txt";
    String HTML = "html";

    public boolean accept(File file) {
        if(file.isDirectory()) {
            return true;
        }
        String ext = getExtension(file);
        return ext.equals(JAVA) || ext.equals(TXT) || ext.equals(HTML);
    }

    private String getExtension(File file) {
        String s = file.getPath();
        int dot = s.lastIndexOf(".");
        if(dot > -1 && dot < s.length()) {
            return s.substring(dot+1);
        }
        return null;
    }
}

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Quote:

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return null;

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That will throw a NPE in
ext.equals(JAVA)
better to use
JAVA.equals(ext)