Presents your 
JAVA E-NEWSLETTER for October 28, 2002

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REMOVE FILES RECURSIVELY

Deleting a directory that contains files is not as uncomplicated as
simply creating the File object and invoking delete(). To safely delete 
a nonempty directory in a platform-independent way, you need a small
algorithm, which removes the files and then removes the directories 
from the bottom of the tree of directories upwards.

To empty a directory of files, you simply loop over the files in the
directory and call delete:

static public void emptyDirectory(File directory) {
    File[ ] entries = directory.listFiles( );
    for(int i=0; i<entries.length; i++) {
        entries[i].delete( );
    }
}

This simple method can be reused in a more powerful way to delete a
whole directory structure. It should recursively call deleteDirectory
whenever it encounters a file that is a directory while looping. The 
method also should check that the argument passed in is actually a directory.
Finally, at the end, it should delete the directory that was passed in.

static public void deleteDirectory(File dir) throws IOException {
    if( (dir == null) || !dir.isDirectory) {
        throw new IllegalArgumentException(
                  "Argument "+dir+" is not a directory. "
              );
    }

    File[ ] entries = dir.listFiles( );
    int sz = entries.length;

    for(int i=0; i<sz; i++) {
        if(entries[i].isDirectory( )) {
            deleteDirectory(entries[i]);
        } else {
            entries[i].delete( );
        }
    }

    dir.delete();
}

If you are coding in Java 1.1 or some variants of J2ME/PersonalJava,
then there is no File.listFiles method. Instead, you will need to use
File.list, which returns an array of Strings, and construct a new File 
object around each String.

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