Whenever we create an array of a non-primitive datatype, that array is by default populated w/ null
values.
Therefore we need to repopulate such array w/ instances of that datatype before using it:
static final int LISTS = 5;
final IntList[] lists = new IntList[LISTS];
{
for (int i = 0; i < LISTS; lists[i++] = new IntList());
}
void setup() {
printArray(lists);
println();
lists[3].append(8);
println(lists[3]);
println(lists[3].get(0));
exit();
}