Java Lesson 2 | Variables

Hey, this is Jake. I'm a special guest on Mac Heads 101, and today I'm going to be talking about variables in Java.

So, I'm going to open up Eclipse. What a variable is, is it's basically something that stores some information. There are two parts to it essentially: the data type and then the name. The name is just to reference it, and you can pretty much use any name you want, except it can't have spaces in it, and you can't start with a capital letter.

I'm going to be talking about four different data types in this tutorial. The first is int. So, to do that, you type int, and I'll call it whole number because that's essentially what an INT is. Int can only store the values of whole numbers; it can't store values with decimals. So, to give it a value, I use equals 10, and I could make that equal any integer I wanted.

The next one I'm going to show is double. You write double, and I'll call that decimal number because that is a decimal. I can set that equal to something like 5.32, and that’s fine. If you set it to 5.32, you would get an error; I'm just going to show you that right now. See? Because it has to be a whole number.

The next one I'm going to be showing you is char, which is a single character like a letter. So I'll call it char letter equals, and then in single quotes, whatever you want. So I'll make that equal to 'B'. Then, if you want to do multiple letters, like if you want to do a phrase, you have to do string. String starts with a capital 'S'. So, string I'll call it phrase equals, and then in double quotes "maads 101".

All right, so now there's the form I'm going to be showing you. If you want to print out a variable, what you have to do is it's pretty simple. If you're just printing out a variable, by the way, always end a line of code with a semicolon.

So, let's say I wanted to print out the phrase "Mac has 101". So I just put phrase in there, and that will print out the value because if I do it without quotes, it'll print out the value of that variable. See? "Mac has 101".

And if I wanted to print out a phrase and a variable, you have to do this. So, I'll just, in these quotes, I'll put "Hello, this is", and then I'll put a space because there's going to be another word. I have to put plus, and that will print out "Hello, this is" plus "maads 101".

And that's how you do some text and variables. So, here: "Hello, this is maads 101". There we go!

You can also do math here. So I could have int wholeNumber equals 10, double decimalNumber equals 5.32, and then I could have another double called sum equals wholeNumber plus decimalNumber. If I print that out, it'll print out the value of wholeNumber plus decimalNumber, which is 15.32.

So now, you can do plus, you can do minus. If you want to multiply, you have to use an asterisk, and that would multiply the two. So I'll just print that out; I'll show you then multiply the numbers.

To divide, you use a slash like that, and that's division. There's a lot more math stuff you can do, and I'll be making another tutorial on that. But you actually have to import something; you have to import java.lang.Math to use a lot of them.

But that is all for variables. So, see you next time!