When you are writing large numbers 1000000000 isn't very
visually distinct from 10000000000.
To help with the legibility you are allowed to insert underscores between digits in an integer literal.
~void main() {
int x = 1_000_000_000;
int y = 10_000_000_000;
IO.println(x);
IO.println(y);
~}This works with hexadecimal integer literals as well.
~void main() {
int white = 0xFF_FF_FF;
IO.println(Integer.toHexString(white));
~}