Very confused...

I took your advice and got rid of it and it compiles now, but it doesn't do anything else. I've continued to mess around with it but I haven't gotten anywhere, so I think it comes down to me not understanding how 'for' loops work. Can you tell me why the (x % 2== 0) doesn't work when (i < 3) works in the example? That is the only difference I can see between them, is it because you can't have an 'if' statement in the conditions for a for loop? for (int i = 0; i < 3; i++) { System.out.println(i); }

A for loop takes 3 optional arguments. The first is a line of code to start the loop, usually used to initialize a counter variable. The second is a conditional statement for the loop to use at the beginning of each new loop cycle; as long as this statement is true the loop continues. The last is a line of code that is run at the each of end cycle, typically to increment the counter. Your confusion is the conditional statement. The loop only continues when this evaluates to true and breaks the loop when it evaluates to false. Because you start the variable x at 1 and the conditional is x % 2 == 0 (which is true only for even numbers), the loop breaks without running a cycle. I think what you are trying to do is this:

for (int x = 1; x <= 15; x++) {
   if(x % 2 == 0)
      System.out.println(x);
}

But you can very simply do this instead:

for (int x = 2; x <= 15; x+=2)
   System.out.println(x);

Ah, that makes sense. Could you explain your second example as well? How does (x+=2) do the same thing as (x % 2 == 0)?

the first part of the for loop starts x at 2. Every loop cycle it increases x by 2. So if it starts at 2 and increases by 2 each loop cycle you get: 2, 4, 6, 8, 10, 12, 14

So instead of checking every number to see if it's even it x can only be even numbers so it doesn't have to check?

There are always multiple ways to solve any problem.