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Wednesday, November 28, 2012

Dino Programmers Need Not Fear Java

While most of this blog focuses on assisting beginning programmers to learn Java as their first computer language, I also try to make it useful to those who are "old school" programmers, like myself, that want to make the transition to the newer language.

I was an accomplished programmer in many procedural and functional languages before I came to any of the Object-Oriented languages. In fact, my favorite language was Modula-2, which worked so well for me doing everything that OO languages were said to do, that I didn't make the transition to OO until about 1994 (a bit late in the game for those who were supposedly active in taking up new languages back then.)

Tools Getting in the Way of the Work
When I came to OO, I had a real hard time learning the whole OO "thing". Much of it looked no different than language structures that enforced normal coding practices used elsewhere. Other parts of it just looked like un-needed restrictions on data access. It was very frustrating.

Part of what slowed my transition to OO had nothing to do with the languages, however. The tools were new, too. That is, I was trying to do things as I was advised to by those more experienced than myself. Rather than using my usual technique of starting out with a text editor and command line compiler and linker, I allowed myself to be talked into going whole hog on IDE interfaces I wasn't familiar with. Once I was in them, I did get some information from them as I worked that helped a bit. But they kept me from really understanding the languages themselves for about a year longer (when nibbling at them part time outside my usual work) than it would have otherwise.

Welcome, Fellow Dinos!
When I started this blog, I strongly considered focusing it on other programmers like myself trying to get comfortable with the move from older languages and programming styles. By the time I did, I was actually pretty comfortable with several OO languages and many development environments and tool chains. But I could still feel the tug of Turbo Pascal when I got frustrated, or plain old vi and make with cc and a system-appropriate linker behind it.

In fact, I still do. There are a fair few nights I unwind by firing up my Ampro Little Board Z-80 system, which runs CP/M 2.2, and having at Turbo Pascal or ASM. Just for relaxation.

It's like embroidery or quilting for aging nerds, I guess.

Java for Dinos
I'm good with being called a dino, so I hope it doesn't put you off if you're an old-timer, too. (Am I really an old timer now? Some folks say so.)

Java is really awfully easy to use at the command line. Create a source file with your favorite text editor.* Open up a command line (no matter what OS you're on), cd to the directory where you saved the file, and compile it with:
javac filename.java

Replace filename with your file's name, of course.
At this stage you need to include the .java file extension. It will produce a new file with the same name but a .class extension is on it now.

Once it completes successfully (and if it doesn't, and old timer should be able to read the error messages and line numbers to fix the code), use the following to run your program:
java filename

Note that even though you're running a .class file, you don't specify the file extension for the java runtime. You'll get an error that makes it look like there's something wrong with your file if you do:
>java Howdy.class
Exception in thread "main" java.lang.NoClassDefFoundError: Howdy/class
Caused by: java.lang.ClassNotFoundException: Howdy.class
 at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
 at java.security.AccessController.doPrivileged(Native Method)
 at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
 at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

And, if you go to compile your program and get really, really long lists of errors, don't be discouraged. Remember the old maxim--fix the first error. Chances are most or all of the rest are errors that cascaded from the first one.

Why Bother?
Java will get you a lot of code that you'd have to write yourself otherwise. Now, this isn't unique to Java these days, it's become the norm for many languages. But you won't find yourself creating a socket driver or string handling routines. Plus, you can treat Java as either a procedural or functional language if that suits you. I did for the most part until about five years ago or so. I got a lot of work done with it, even at that.

But, I moved on to using Java "as it was meant to be" over time, because it meant rewriting less code, or less work re-using code. I just took getting there one step at a time. Learning how to do everything I did fluently in Modula-2, or LISP, in Java. (Or one of the various Pascals, or C, etc.) Libraries, general purpose re-usable code, flexible data structures, and so on.

Come In and Look Around
Have a look at my Basic Java Articles, listed in the right column. I strive to post actual working code in my examples, in the form of complete programs. So you don't have to guess about how to fit a snippet into your code.

To do this, I often strip away code that would be good to have, but which might cloud the issue. So I don't guarantee that my examples are good coding practice, but only that they are complete working examples of what I'm talking about. And I warn you in the article when it's not the greatest. Full code can also be downloaded from my Java code repository for this blog (also on the right side of every article here.)

If my articles are of use to you, or you think I can improve things, drop me an email.

Thanks.

*I still do a lot of coding in plain old vi, though I've gotten to like the syntax highlighting in vim as well. If I want an IDE, I usually prefer one of the simpler ones like BlueJ or Greenfoot, though I can bury myself complex ones like Eclipse or NetBeans if I really want to. Occasionally I fire up emacs, though I prefer a stripped version of that, too.


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