array_test.java

// Example of how to find indices to values in a 2D array that are below a specified index.
/*
  Take the following
  [0,1,2,3
   4,5,6,7
   8,9,10,11]
   
   This formula helps you figure out, for instance, what the index of 4 is if we're looking at index 0.
   
   
   This was done in Processing www.processing.org
*/



int cols = 4;
int rows = 3;

ArrayList vals = new ArrayList();
void setup(){
  
  
  
  for(int i = 0; i < cols; ++i){
     for(int j = 0; j < rows; ++j){
  
       vals.add(new PVector(random(10),random(10)));
       
     }
  }
  println(vals);
  println("\n");
  
  // the current index to look at
  int currentIndex = 0;
  
  // how far down the array we want to look at. 
  int howFarBelow = 1;
  
  // get that index
  int below = currentIndex + cols * howFarBelow;
  
  // this should be the value that is below 0, or 4 in this case
  println(vals.get(below));
}