This is a graded exercise which should be posted to your learning journal. The sample program DirectoryList.java (in the code directory), given as an example in section 11.2.2 of the textbook will print a list of files in a directory specified by the user. But some of the files in that directory might themselves be directories. And the subdirectories can themselves contain directories. And so on. Write a modified version of DirectoryList that will list all the files in a directory and all its subdirectories, to any level of nesting. You will need a recursive subroutine to do the listing. The subroutine should have a parameter of type File. You will need the constructor from the File class that has the form

public File( File dir, String fileName ) // Constructs the File object representing a file // named fileName in the directory specified by dir.

SAMPLE PROGRAM

import java.io.File;

import java.util.Scanner;

/**

* This program lists the files in a directory specified by

* the user. The user is asked to type in a directory name.

* If the name entered by the user is not a directory, a

* message is printed and the program ends.

*/

public class DirectoryList {

public static void main(String[] args) {

String directoryName; // Directory name entered by the user.

File directory; // File object referring to the directory.

String[] files; // Array of file names in the directory.

Scanner scanner; // For reading a line of input from the user.

scanner = new Scanner(System.in); // scanner reads from standard input.

System.out.print("Enter a directory name: ");

directoryName = scanner.nextLine().trim();

directory = new File(directoryName);

if (directory.isDirectory() == false) {

if (directory.exists() == false)

System.out.println("There is no such directory!");

else

System.out.println("That file is not a directory.");

}

else {

files = directory.list();

System.out.println("Files in directory \"" + directory + "\":");

for (int i = 0; i < files.length; i++)

System.out.println(" " + files[i]);

}

} // end main()

} // end class DirectoryList