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For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Flexibility in input - read from file, web resource or keyboard

When you're writing a program, don't think that you're reading from a file - think that you're reading from a stream. That gives you the flexibiity to read from a file, or from a web resource, or from a device such as a keyoard.

A stream is an input flow of data that comes to you, record by record (typically line by line) and each time you call for a record / line to be read, the next one will come to you. And when you reach the end of your data, you'll get back some sort of end-of-file signal to tell you that you're done.

Towards the end of last week's (Java) course, I wrote an example (source [here]) which would read either from a file, or from a URL (web resource / page). The initial opening of the resource differs, but once I have my Input Stream Reader, or a subclass of it, I can then use common code to handle the buffering of the data and the passing back of it to my application line by line.

In order to make the example clear, I didn't do anything fancy on the resource name the user types in to see if it looks like a file name or URL - I have him specify. Here's my resource opening code:

  import java.io.*;
  import java.net.*;
  try {
    if (args[0].equals("w"))
    instream = new InputStreamReader((new URL(args[1])).openStream());
    if (args[0].equals("f"))
    instream = new FileReader(args[1]);
  } catch (Exception e) {
  if (instream == null) {
    System.err.println("Usage: java Stations w|f url|filename");

Common code then sets this stream up to be buffered, so that I can read it line by line:

  BufferedReader source = new BufferedReader(instream);

And further common code allows me to loop through the resource while data is still available:

  String lyne;
  while ((lyne = source.readLine()) != null) {

(written 2015-02-08, updated 2015-02-12)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
J808 - Java - Network Programming
  [1976] Where is this IP address, IPv4 and IPv6 - (2009-01-04)
  [2863] Writing a server in Java - (2010-07-09)

J713 - Java - More Input and Output
  [1239] End of File on a Java BufferedReader - (2007-06-22)
  [2420] Exceptions in Java - why and how - (2009-09-24)
  [4350] Keyboard reader for Java programming newcomers - (2014-12-12)
  [4414] Java - converting an integer to a fixed length string - (2015-02-04)

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Some other Articles
Looking Forward - TransWilts Community Rail Partnership and TransWilts CIC
Campus - about the logos / way marks you have been choosing from
Objects - from physical to virtual or abstract - Java
How healthy are the stars of stage and screen?
Flexibility in input - read from file, web resource or keyboard
Java Inheritance example - group of classes - step by step
Melksham Community Campus - which of these potential signs do you like?
Crisp morning, fast run
Challenging the IT course business model
Buffet review - taking the price into account
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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