In my
last post I mentioned that I had been writing an instructional applet for my son to learn some math concepts. I received this half-joking reply:
If you truly loved your son, you would have made HIM program that applet! He's seven - that's old enough for Java, at the very least.
I actually think seven is a little young to get started, but as I thought about it, I decided, heck, why not? I picked up some extra money in college tutoring a thirteen year old in C++, and later taught classes for half a year in Fort Worth. It's been over ten years since I taught any actual classes, but is it all that unreasonable to try and give the essential concepts of Java across to a seven year old?
I was already six when my dad bought our
first computer, and it wasn't for a few more years that I started reading and understanding the
BASIC programs that were in vogue back then. But Ben, like many kids of his generation, was introduced to computers at an early age, and has been comfortable using them for most of his life. He's already seen what the inside of a computer looks like when I swapped out components, and I've even gone over some explanations of binary numbers with him, including the "
counting on your fingers" trick.
I have done two lessons so far, first on paper and last night on a laptop. Since I've done only sporadic posts on this blog recently, I think it's not a bad idea to chronicle some of this effort. One thing I discovered while teaching classes is that there is no better way for you to solidify fundamental concepts in your own mind than to try to explain it to somebody else. There is nothing like having to break down assumptions that are second nature to you but completely foreign to another person.
So the first thing I've discovered is: Java is kind of hard.
Programmers traditionally write "Hello world" as their first program, so let's take a look at some ways that this is handled in various languages.
BASIC:
10 print "Hello world"
Nobody learns BASIC anymore, but it was a standard on those old PC 8086's I had as a kid. In fact, if you booted up the computer without inserting a floppy disk, the computer (which lacked a hard drive, and hence lacked a useful operating system in memory) would just load up a BASIC compiler environment directly from the
BIOS. It was designed to be a beginner language.
Next let's look at Perl, which is known as a scripting language that is powerful at handling string manipulation:
print "Hello world";
Even simpler, superficially, because Perl is a procedural language which does not use line numbers. Once you start getting into program flow, BASIC starts looking simpler through heavy use of the "goto" statement to control program flow. But as everyone should know, "goto" sucks.
Next we'll look at
C, which is what I initially taught in the semester before teaching my classes C++.
#include <stdio.h>
main() {
printf("Hello world");
}
Slightly trickier. In C, nothing runs unless it is directly or indirectly invoked by a "main" function. Thus, unlike the other two languages, in order to become proficient enough to run the most trivial of programs, you have to have some trivial understanding of what a function is about.
There's also the rather cryptic line "#include <stdio.h>", which contains additional wacky symbols that have to be either explained or hand-waved away. When I introduced students to this language, I initially just gave them a complete "hello world" program and said "Focus on what's inside the braces, you'll understand what they mean later." Students love to complain about this sort of thing, as they tend to view unexplained stuff as unnecessary and annoying.
Now
here's the java program.
class Hello {
public static void main(String[] args) {
System.out.println("Hello world");
}
Seriously now, those are a LOT of details to expect a pure novice to absorb, even if he were older. Let me count the unfamiliar concepts:
- "class Hello": Right from the get-go, all Java programs enforce object-oriented structure. Objects and classes are a beast to understand -- I first heard the concept as a senior in high school, failed to self-teach it, and then didn't really get it until my first college course in C++. Now let's explain the difference between a class and an instantiating object to kid who's going on eight.
- "main": Just like in the C example, you're not going to get anywhere until you understand methods (aka functions inside a class). I had to make an analogy to nouns and verbs in sentences, since Ben has played Mad Libs before. Even so, it's all pretty abstract, and the word "main" does not suggest an action word at all.
- "(...)": Now that we know that "main" is a verb, it's time to learn that all verbs in Java must be followed up with parentheses, which may or may not contain some arguments.
- "void": Some methods return an object type and others don't... you know what? I'll tell you later.
- "public": So here we encounter the notion of public and private methods, which is intended to separate interface from implementation. Simple, right?
- "static": So yeah, this function can be called generically through the class itself, and does not need to be applied to a particular instance of the class. And by the way, all methods called directly from "main" must also be called "static," and the only way to simplify your calls is if you declare a second class and make an instance object.
- "String ... args": It's an object declaration. A string is a sequence of characters. Your program won't recognize the "main" method unless that String argument is in there, even though we have no intention of reading the command line arguments yet...
- "[]": ...but this string is not just any old single string, it's actually an array of strings, which means there can be any number of them sequentially, see?
- "System.out.println": These are not even a proper part of the language definition. They are objects that are accessed by loading in the standard Java libraries, and they actually have a bunch of additional code written to accomplish their task somehow, but you will never see that code. You just have to accept that it will work as a "black box" that does what you expect. And then there's the idea that "System" contains an object called "out" which has a method called "println", where even the last word is not as easy to understand as plain old "print".
- All the syntax: This is probably second nature to every programmer by now, but just try to think about how you would explain and reinforce the idea of all the funny characters and when to use them. Quotation marks must signify string literals. Parentheses are required for both declaring and calling methods. Semicolons must end all statements, but NOT the method declaration (I don't know for sure if he ever saw a semicolon before). And, again, what the dots mean in between "System", "out", and "println".
That's quite a lot to bite off just to write two words. And by the way, when I try to get into inputting text, the proper format will be something like this:
String name = "";
InputStreamReader input = new InputStreamReader(System.in);
BufferedReader reader = new BufferedReader(input);
try {
name = reader.readLine();
} catch (Exception e){};
Compare that to
INPUT "Input name: ", name$
in BASIC, and
$name = <>;
in Perl.
Nevertheless, we heroically slogged through that stuff, discussing some parts in detail and skipping over other parts. Then we finally got to String variables.
No input yet, and no kind of string manipulation or concatenate. Just
String name = "Ben";
followed by
System.out.print("Hello ");
System.out.print(name);
Had a tough time getting him to see that the second print statement would print "Ben" rather than "name," and why.
As far as I can tell, I still have his attention and he wants to keep at it. He would like to write a graphical game, but I told him he has a lot to learn about text-only programs
first before we can start to cover that. I know a lot of graphics, but much of it requires knowledge of not only Cartesian coordinates but also trigonometry. Believe me, I'm not touching trig.
A couple of open questions for readers:
- Was it a mistake to start in Java?
- If not, why not?
- If you were being introduced to programming for the very first time, which language would you want to be taught first?
- Crazy thought: Ben has a bunch of favorite sites stuffed with Flash games. He even said that he wished he could make one someday, which prompted me to say that it's too advanced for now. I have never learned Flash myself. Is it easy? Is it free? Would it be better or worse than Java as a "first time" language?
