Directory listing, file i/o and formatting demo

this example from a Well House Consultants training course
More on this [link]

This example is described in the following article(s):
• Exceptions in Java - why and how - [link]

Source code: Yvonne.java Module: J050

import java.io.*;
import java.text.*;

/*
*/

public class Yvonne {

public static void main (String [] args) throws IOException {

// Without parameters, do a directory listing

        if (args.length == 0) {
                File current = new File(".");
                String [] things = current.list();
                for (int i=0; i<things.length; i++) {
                        System.out.println(things[i]);
                        }
                System.exit(0);
                }

// If not a listing Check that we have exactly two parameter

        if (args.length != 2) {
                System.err.println("Usage line ...");
                System.exit(2);
                }

// Check that the parameter IS the name of a file that exists

        File Source = new File(args[0]);
        if (! Source.exists()) {
                System.err.println("Input file not available");
                System.exit(1);
                }

// Looks good, so open it for read

        BufferedReader DataInput =
                new BufferedReader(new FileReader(Source));

        int matched = 0, all = 0;

// Open an output file too

        FileWriter SafetyNet = new FileWriter("latest.tmp");

// Go through the file, line by line

        while (true) {
                String stuff = DataInput.readLine();
                if (stuff == null) break;
                all++;
                if (stuff.startsWith(args[1])) {
                        System.out.println(stuff);
                        SafetyNet.write(stuff + "\n");
                        matched ++;
                        }
                }
        SafetyNet.close();

        float pcmatched = matched * 100.0F / all;
        System.out.println("Matched "+matched+" of "+all);
        System.out.println("Matched to "+pcmatched+"%");

// Oops - that's over-accurate so let's format it!
// May as well do it the same way we would format money!

        DecimalFormat money = new DecimalFormat("###0.00");
        String pc2dp = money.format(pcmatched);
        System.out.println("Matched to "+pc2dp+"% of records");

        }
}

/*

---------- Sample Output

A REGULAR CALL

Dorothy-2:java grahamellis$ java Yvonne access_log.xyz catfish
catfish - - [28/Aug/1998:09:47:39 -0400] "GET /index.html HTTP/1.0" 200 1476
catfish - - [28/Aug/1998:09:58:34 -0400] "GET /index.html HTTP/1.0" 200 1476
catfish - - [28/Aug/1998:09:59:41 -0400] "#GET /perl/index.html HTTP/1.0" 501 -
catfish - - [11/Dec/1998:09:25:44 -0500] "GET index.html HTIP/1.0" 400 -
catfish - - [11/Dec/1998:09:27:25 -0500] "GET /index.html HTTP/1.0" 200 1476
Matched 5 of 6912
Matched to 0.07233796%
Matched to 0.07% of records
Dorothy-2:java grahamellis$

A CALL THAT IS WRONG

Dorothy-2:java grahamellis$ java Yvonne access_log.xyz
Usage line ...
Dorothy-2:java grahamellis$

THE SPECIAL CALL THAT LISTS THE DIRECTORY

Dorothy-2:java grahamellis$ java Yvonne
access_log.xyz
Adam.class
Adam.java
Bernie.class
Bernie.java
Chloe.class
Chloe.java
Daniel.class
Daniel.java
disney
Edward.class
Edward.java
Fred.class
Fred.java
Glenda.class
Glenda.java
Hilary.class
Hilary.java
Irene.class
Irene.java
Julie.class
Julie.java
Keith.class
Keith.java
latest.tmp
Lenny.class
Lenny.java
Margaret.class
Margaret.java
Niamh.class
Niamh.java
Orlando.java
Peter.class
Peter.java
Quentin.class
Quentin.java
Rolf.class
Rolf.java
Steve.class
Steve.java
Time.class
Time.java
TimePlus.class
TimePlus.java
Trevor.class
Trevor.java
Ulrika.class
Ulrika.java
Viv.class
Viv.java
WellHouseInput.class
WellHouseInput.java
Wendy.class
Wendy.java
Xena.class
Xena.java
Yvonne.class
Yvonne.java
Zoe.class
Zoe.java
Dorothy-2:java grahamellis$

*/

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