ArrayIndexOutOfBoundsException?

Programming Questions

ahhreeyell

ArrayIndexOutOfBoundsException?

in Programming Questions • 2 years ago

I copied this code straight from a Processing book, and yet whenever I try to compile, I keep receiving a message stating: ArrayIndexOutOfBoundsException = 0. Anybody know why?

float[] sineWave = new float[width];

void setup() {

}

void draw() {

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

float r = map(i, 0, width, 0, TWO_PI);

sineWave[i] = abs(sin(r));

}

for(int i=0; i<sineWave.length; i++) {

//Set the stroke values to numbers read from the array

stroke(sineWave[i] * 255);

line(i, 0, i, height);

}

Replies(3)

algo_macc..

Re: ArrayIndexOutOfBoundsException?

2 years ago

Hi,

you need to define width before to use it.

It could be look like that :

Copy code

float[] sineWave;
void setup() {
size(200,200);
sineWave = new float[width];
}

+++

ahhreeyell

Re: ArrayIndexOutOfBoundsException?

2 years ago

Sweet, thank you so much! One more question: why do I need to create the array in setup()? Why can't I create it outside of the setup() and draw() functions?

noncom

Re: ArrayIndexOutOfBoundsException?

2 years ago

Because in Processing the 'width' variable is reserved for sketches screen width. And it gets actually defined only after the size() statement (in your example it becomes equal to 200). This is why you can use it only AFTER size(). You can try to initialize the array outside setup() (before it) if you use some custom defined variable.

Copy code

int myvar = 200;
float[] sineWave = new float[myvar];

Or just use a number (which is not recommended):

Copy code

float[] sineWave = new float[200];

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