Java Lesson 8

Hey guys, this is Mac. Heads in the one with our last Java lesson.

So, as you may know, after this Java lesson, we're going to move into Mac programming. But anyway, I'm going to do our last Java lesson once and for all. In this Java lesson, I'm going to be teaching you classes and how to call methods on other classes, how to declare classes, how to make classes, etc.

I'm going to open up Xcode. I'm going to create a new project. I'm going to make it Java, you have a tool, and I'm going to call it Classy App. I'll save it to my desktop. So right here, you know, you've been editing Classy App or whatever the name of it is, dot Java. Inside of that is public class Classy App.

What you may not realize is you can make other classes as well. If I right-click on this Classy App class and say new file, and I go to pure Java, Java class, I will call it PrintOutFunctions. Then I can put a public static void on this, just say printName, and then I'll say string name. All this will really do is print line "Hello, name," and that's all it'll actually really do.

But if you take a look at this, how do we call that function on that other class? Well, the answer is simple. Now that you have another class here, and as you can see, it is called PrintOutFunctions, we can just use it like it's a variable. We say PrintOutFunctions space, I'll call pof space, and now you need to make it new PrintOutFunctions, left parenthesis, right parenthesis, semicolon to make a new one.

Now, I'll say pof dot and then whatever we call the function. I think it's printName, and I'll just print the name "Mac Head's a little one." And now I'll get rid of this because we don't really need this. But now watch—hello, Mac Kids, everyone!

So as you can see, we can organize our code. So we can have a class that all it does is do random print things. We can make it so, instead of needing to do system.out.printline, I'll make my own thing in here called printf that'll just run system that have that print. So this way, now if I want to print something, say pof dot print, they'll say "Hi," and I have to manually type backslash n to do a new line because I'm not using print line, I'm just using print. So I'm printing "Hi" right there.

So in this lesson, I've just taught you how to use classes. So I can also put other functions on this class. And here's another cool thing you may know about private functions. Here’s what this private function is: a private function is something that can't be accessed from the outline outside.

So here, I can just do printfp right here. And the interesting thing is that right here, I have this void called printfp, but I will not be able to see that from here. So if I do pof dot printf, it will show up and work; but if I do print fp "Hi," it will not work properly. See? It has private, so you cannot access it from another class.

That goes the same for variables. If I make it public, it's x in a public into y. What I can do from here is I can say pof.x equals maybe 10, pof dot y equals 10. And it'll work perfectly. And of course, we're not printing anything out or anything. But if I make these variables private, then it will not work.

Now another thing I'm going to show you is how to use this more efficiently. So basically, a variable or a class can have methods or functions on it as well as variables. So here's an x and a y. What I'm going to do, I'm going to only have one pof, but it's going to be storing me 2 inches. So that's a way to like save yourself code from declaring two inks.

Um, this way, I can just do pof dot print y plus y, x plus x, and then I'll do another next session. The way this will work is it'll print out 10, 10, and I'll make this 12 or 14 or whatever. Oh, sorry, I forgot to do pof.xml, my fault, totally sorry. So there we go, and it says, "So be ready for Objective C next. Goodbye!"