Array help

wolfrog

I am trying to populate an array with all of the x values I am going to be using in a program, but it keeps returning an error saying that my array is empty

this is a global variable at the top of my code:

int x_length = (width/25);

this is the for loop I am using to try and fill all of the iterations of the array. I am ultimately trying to create 25 different points along the x axis that are spaced at a distance of (width/25) from one to the other

int[] x_points = new int[x_length];

for (int i=0; i <= 25; i++) {

  x_points[i] = x_length * i;

  println("int val : x_points");

}

when I run the code, the program works for about 2 seconds and then highlights 'x_points[i] = x_length * i;' and returns the ArrayIndexOutOfBoundsException: 0 message, but i am having trouble figuring out why it's saying my array is empty?

quark

The problem is because the for-loop assumes that there will be 26 elements (0 to 25 inclusive) in the array change the loop to

for (int i=0; i < x_points.length; i++) {
  x_points[i] = x_length * i;
  println(i + "   "  + x_points[i]);
}

The length field of an array always holds the number of elements in it so it is a safe way to limit the array index to prevent ArrayIndexOutOfBoundsException

wolfrog

Okay thanks that helps, I don't get any error messages when I replace with your suggestion, but for some reason the for loop is never being initialized. It could be because I am using that for loop to iterate the values within the array x_points so it starts with a value of zero and therefor never starts... so I changed the test statement to be =< and the for loop initializes...

and then I am back to where I started, I get the same error message, OutOfBoundsException: 0, on the

'x_points[i] = x_length * i;' line again

GoToLoop

OutOfBoundsException: 0

It means the array is 0-length! You need to specify a bigger size than that when creating the array! :-\"

quark

int x_length = (width/25);

At the top of your code width has the value 0 so you end up with a zero length array. Change this line to

int x_length;

THEN include the statement x_length = (width/25); in the setup function AFTER you have called the size(...) function

THEN change the loop back to my previous post, do NOT use <= otherwise you will get the ArrayIndexOutOfBoundsException back