Need help with NPE?

Programming Questions

spectre.h..

in Programming Questions • 10 months ago

Here is the code where it is happening:

//Up in the global declarations:
color[] colors;
void setup(){
//Stuff in here
createColors();
}
void draw(){
//Stuff in here
}
void createColors(){
int var1 = height/50;
int var2 = width/100;
for(int i = 0; i < var2; i++){
for(int j = 0; i < var1; j++){
float r, g, b;
r = random(255);
g = random(255);
b = random(255);
color newColor = color(r, g, b);
colors[i+j] = newColor;
}
}
}

In line 26 of the above code, I get a NPE.

Instead of line 25 and line 26, I have tried the alternative options and I still get the same NPE:

colors[i+j] = color(r, g, b);

And also manually:

colors[i+j] = color(255, 255, 255);

If anyone could please point out my errors, I would much appreciate it!

Thank You

Replies(3)

velvetkev..

Re: Need help with NPE?

10 months ago

You need to initialise colors[] before trying to fill it:

colors=new color[x];

Where x is the number of colours you need.

spectre.h..

Re: Need help with NPE?

10 months ago

Thank You.

However, I do have a question:

What if I don't initially know how many I need? Like if it is dependent on some environmental variables?

GoToLoop

Re: Re: Need help with NPE?

10 months ago

What if I don't initially know how many I need?

In that case, the most recommended, is to use ArrayList in place of normal Arrays[].

For normal array we have for example:

byte colorsNum = 10;
color[] myColors = new color[colorsNum];

The same as an ArrayList:

List<color> myColors = new ArrayList();

As you can see, a List does not need a fixed number of items beforehand as a normal array does.

But its syntax is a little more complicated:

Adding an element to a List:

myColors.add(#FF00FF); //add a new color number into the ArrayList myColors.

Reading an element from a List:

fill( myColors.get(5) ); //read 6th color element from ArrayList myColors and use it for fill().

For more information, look at this following link -> ArrayList

That's all for now!

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