code: private void pruneMatches() {
  		int index = 0;
  		while( index < matches.size ) {
  			AssociatedTripleIndex a = matches.get(index);
  			// not matched. Remove it from the list by copying that last element over it
  			if( a.c == -1 ) {
  				a.set(matches.get(matches.size-1));
  				matches.size--;
  			} else {
  				index++;
  			}
  		}
  	}
docs: Removes by swapping all elements with a 'c' index of -1