# How to run half element of array length
**URL:** https://discourse.processing.org/t/how-to-run-half-element-of-array-length/12439
**Category:** Processing
**Created:** [July 2, 2019, 10:29am UTC](https://discourse.processing.org/t/how-to-run-half-element-of-array-length/12439 "2019-07-02T10:29:15Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@The\_nish](https://discourse.processing.org/u/The_nish)
#### Post date: [July 2, 2019, 10:29am UTC](https://discourse.processing.org/t/how-to-run-half-element-of-array-length/12439/1 "2019-07-02T10:29:15Z")
i have 50 images and i want to run sequential each image in my folder and what i am trying to do is that i am creating an array of 100 images.but i have only 50 image and other 50 images Add in a sequence when program is running and.
i want auto running array which read value if value is available .
just like if array running 50 images if it encounter 51 image then it should be run in next loop.each time i want to do that.
and when i trying to do that i get NullPinterException. so tell me what should i do.
```auto
int maxImages = 100;
PImage[] images = new PImage[maxImages];
for (int j = images.length-1; j >= 0; j-- ) {
if(images[j] == null)
{
maxImages++ ;
}
images[j] = loadImage( "img"+j+".png" );
frameRate(1);
}
}
```
---
### Author:  [@GoToLoop](https://discourse.processing.org/u/GoToLoop)
#### Post date: [July 2, 2019, 4:28pm UTC](https://discourse.processing.org/t/how-to-run-half-element-of-array-length/12439/2 "2019-07-02T16:28:56Z")
```auto
// Discourse.Processing.org/t/how-to-run-half-element-of-array-length/12439/2
// GoToLoop (2019/Jul/02)
static final String NAME = "img", EXT = ".png";
static final int IMAGES = 100, PRELOAD = 50;
final PImage[] images = new PImage[IMAGES];
int idx, total = PRELOAD;
void setup() {
size(1200, 600);
frameRate(1);
for (int i = 0; i < PRELOAD; )
images[i] = loadImage(NAME + i++ + EXT);
}
void draw() {
background((color) random(#000000));
set(0, 0, images[idx = (idx + 1) % IMAGES]);
if (total < IMAGES)
images[total] = loadImage(NAME + total++ + EXT);
}
```
---
### Author:  [@jeremydouglass](https://discourse.processing.org/u/jeremydouglass)
#### Post date: [July 4, 2019, 11:07pm UTC](https://discourse.processing.org/t/how-to-run-half-element-of-array-length/12439/3 "2019-07-04T23:07:44Z")
Another option is to use an ArrayList, and add newly loaded images to the end of the list. Then looping through the list by its length will never encounter nulls – the list is always as long as its number of entries, and it grows as you add: 51, 52, 53… 99, 100.
[https://processing.org/reference/ArrayList.html](https://processing.org/reference/ArrayList.html)