Array index out of bounds exception: 100 - processing

Question

//----------------------------------------------\\
float x = 300;
float y = 300;
float direction = 0;
float increment = 1;
float speed = 5;
boolean toggle = true; // - For spaceship reversal
float wormX = random(0, 600); // - For wormHole v
float wormY = random(0, 600);
float wormGrowth = 0;
boolean growthSwitch = true; // - for wormHole ^
float[] starXpos = new float[100]; //starsRandom
float[] starYpos = new float[100]; //starsRandom
float d = dist(x, y, wormX, wormY);
int score = 0;
//----------------------------------------------\\
//----------------------------------------------\\ Setup
void setup (){
size (600, 600);
starsP1();
}
//----------------------------------------------\\ Draw
void draw (){
background (0);
spaceShip();
starsP2();
wormHole ();
score();
warpInitial();
blackHoleAt(100, 40);
blackHoleAt(400, 500);
}
//----------------------------------------------\\
//----------------------------------------------\\ starsRandom
void starsP1(){
int i = 0;
while (i < 100){
starXpos[i] = random(0, width);
starYpos[i] = random(0, height);
i = i + 1;
}
}
void starsP2(){
stroke(255);
strokeWeight(5);
int i = 0;
while (i < 100){
point(starXpos[i], starYpos[i]);
i = i + 1;
}
if (key == 'w'){
starYpos[i] = starYpos[i] + 1;
}
}
I'm trying to create a form of parallax for the stars in my code. When the user presses w,a,s,d the array of stars should correspond to the direction. I don't understand how this should work as I keep getting this error.

Answer 1

Try formatting your code to better see what's going on:
void starsP2(){
stroke(255);
strokeWeight(5);
int i = 0;
while (i < 100){
point(starXpos[i], starYpos[i]);
i = i + 1;
}
if (key == 'w'){
starYpos[i] = starYpos[i] + 1;
}
}
Your while loop executes until i == 100. Then after the while loop exits, you use that i variable again. Since i is 100, and your starYpos array only has up to index 99, you get an error.
The fix is to either move that if statement to inside the while loop, or to refactor your code so i doesn't go outside the bounds of the array.