Looking at a Directory for existence of files (with any extension)

[Mei Jones]

In following code I am expecting Java to make exists = "True" if there is any .doc, .xls, .pdf and many more files.

But it is checking only subdirectories inside the main folder.

What class I should instantiate object "f" from?



boolean exists = f.exists();

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

class FileTest {
    public static void main(String[] args) {
        //-- Make sure there is one parameter
        if (args.length != 1) {
            System.err.println("ERROR: must have 1 parameter");
            System.exit(1);
        }

        try {
            File f = new File(args[0]);
            long d;

            System.out.println("getName()          = " + f.getName());
            System.out.println("getAbsoluteFile().getName() = "
                              + f.getAbsoluteFile().getName());
            boolean exists = f.exists();
            System.out.println("exists()           = " + exists);
            if (!exists) {
                System.exit(1);
            }
            System.out.println("canRead()          = " + f.canRead());
            System.out.println("canWrite()         = " + f.canWrite());
            System.out.println("getPath()          = " + f.getPath());
            System.out.println("getAbsolutePath()  = " + f.getAbsolutePath());
            System.out.println("getCanonicalPath() = " + f.getCanonicalPath());
            System.out.println("getAbsoluteFile()  = " + f.getAbsoluteFile());
            System.out.println("toURL()            = " + f.toURL());
            System.out.println("toURI()            = " + f.toURI());
            System.out.println("getParent()        = " + f.getParent());
            System.out.println("isAbsolute()       = " + f.isAbsolute());
            boolean isDirectory = f.isDirectory();
            System.out.println("isDirectory()      = " + isDirectory);
            System.out.println("isFile()           = " + f.isFile());
            System.out.println("isHidden()         = " + f.isHidden());
            System.out.println("lastModified()     = " + (d = f.lastModified())
                               + " = " + new Date(d));
            System.out.println("length()           = " + f.length());
            if (isDirectory) {
                String[] subfiles = f.list();
                for (int i=0; i<subfiles.length; i++) {
                    System.out.println("file in this dir   = " + subfiles[i]);
                }
            }
        } catch (IOException iox) {
           System.err.println(iox);
        }
    }//endmethod main
}//endclass FileTest

[Jeff Verdegan]

So if your object corresponds to the directory /A/B/C and you want to list all of C's peers--for example, A/B/D.txt, /A/B/E.doc, etc., then you don't want to call list() on C, you want to call it on B. File has a method called getParent() or something like that which gives you the parent directory of the current File object, which is where you want to call list() (if I understand your problem correctly).

[Mei Jones]

Thanks for the reply..

All what I need by checking exists on File object whether the last sub folder is empty or not.

/A/B/C .. if C is the last folder want to know whether C is empty or not. I thought f.exists() will do the trick apparently not..

I like any light on this?

[Paul Clapham]

If you want to know whether a folder is empty, the way to do that is to get the files in that folder into an array, using one of the methods of the File class. If that array is empty, that means the directory is empty.

[Jeff Verdegan]

Mei Jones wrote:Thanks for the reply..

All what I need by checking exists on File object whether the last sub folder is empty or not.

/A/B/C .. if C is the last folder want to know whether C is empty or not. I thought f.exists() will do the trick apparently not..

If your File object corresponds to /A/B/C, then exists() will tell you whether /A/B/C exists. This is stated in the documentation.

If you want to know if C is empty, then you need to to call isDirectory(), and if it's true, call list() or listFiles() and see if it returns an empty array. This is also evident from the documentation.